sphinx: add links for Yocto project website

In DocBook, variables are used to create custom links (note that it is
not consistent everywhere, since some web addresses are still
hardcoded), such as YOCTO_HOME_URL, YOCTO_GIT_URL, YOCTO_WIKI_URL,
YOCTO_BUGS_URL and YOCTO_DL_URL..

In Sphinx they are replaced with extlinks.

(From yocto-docs rev: d25f3095a9d29a3355581d0743f27b2a423ad580)

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/kernel-dev/kernel-dev-advanced.rst

@@ -20,8 +20,8 @@ BSPs and Linux kernel types.
 Kernel Metadata exists in many places. One area in the Yocto Project
 `Source Repositories <&YOCTO_DOCS_OM_URL;#source-repositories>`__ is the
 ``yocto-kernel-cache`` Git repository. You can find this repository
-grouped under the "Yocto Linux Kernel" heading in the `Yocto Project
-Source Repositories <&YOCTO_GIT_URL;>`__.
+grouped under the "Yocto Linux Kernel" heading in the
+:yocto_git:`Yocto Project Source Repositories <>`.
 
 Kernel development tools ("kern-tools") exist also in the Yocto Project
 Source Repositories under the "Yocto Linux Kernel" heading in the
@@ -188,7 +188,7 @@ either
 :term:`FILESEXTRAPATHS` if
 you are creating Metadata in `recipe-space <#recipe-space-metadata>`__,
 or the top level of
-```yocto-kernel-cache`` <&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache/tree/>`__
+:yocto_git:`yocto-kernel-cache </cgit/cgit.cgi/yocto-kernel-cache/tree/>`
 if you are creating `Metadata outside of the
 recipe-space <#metadata-outside-the-recipe-space>`__.
 

documentation/kernel-dev/kernel-dev-common.rst

@@ -286,7 +286,7 @@ section:
 5. *Create a Local Copy of the Kernel Git Repository:* You can find Git
    repositories of supported Yocto Project kernels organized under
    "Yocto Linux Kernel" in the Yocto Project Source Repositories at
-   ` <&YOCTO_GIT_URL;>`__.
+   :yocto_git:`/`.
 
    For simplicity, it is recommended that you create your copy of the
    kernel Git repository outside of the
@@ -1404,7 +1404,7 @@ To help you use your own sources, the Yocto Project provides a
 linux-yocto custom recipe (``linux-yocto-custom.bb``) that uses
 ``kernel.org`` sources and the Yocto Project Linux kernel tools for
 managing kernel Metadata. You can find this recipe in the ``poky`` Git
-repository of the Yocto Project `Source Repository <&YOCTO_GIT_URL;>`__
+repository of the Yocto Project :yocto_git:`Source Repository <>`
 at: poky/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb
 
 Here are some basic steps you can use to work with your own sources:
@@ -1535,7 +1535,7 @@ Linux kernel sources, if you need an external kernel module, the
 create your own out-of-tree Linux kernel module recipe.
 
 This template recipe is located in the ``poky`` Git repository of the
-Yocto Project `Source Repository <&YOCTO_GIT_URL;>`__ at:
+Yocto Project :yocto_git:`Source Repository <>` at:
 poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
 
 To get started, copy this recipe to your layer and give it a meaningful

documentation/kernel-dev/kernel-dev-concepts-appx.rst

@@ -38,7 +38,7 @@ needs for targeted hardware.
 
 You can find a web interface to the Yocto Linux kernels in the `Source
 Repositories <&YOCTO_DOCS_OM_URL;#source-repositories>`__ at
-` <&YOCTO_GIT_URL;>`__. If you look at the interface, you will see to
+:yocto_git:`/`. If you look at the interface, you will see to
 the left a grouping of Git repositories titled "Yocto Linux Kernel".
 Within this group, you will find several Linux Yocto kernels developed
 and included with Yocto Project releases:

documentation/kernel-dev/kernel-dev-intro.rst

@@ -20,10 +20,10 @@ Project, and provides insight into how the Yocto Project team develops
 and maintains Yocto Linux kernel Git repositories and Metadata.
 
 Each Yocto Project release has a set of Yocto Linux kernel recipes,
-whose Git repositories you can view in the Yocto `Source
-Repositories <&YOCTO_GIT_URL;>`__ under the "Yocto Linux Kernel"
+whose Git repositories you can view in the Yocto
+:yocto_git:`Source Repositories <>` under the "Yocto Linux Kernel"
 heading. New recipes for the release track the latest Linux kernel
-upstream developments from ` <http://www.kernel.org>`__ and introduce
+upstream developments from http://www.kernel.org> and introduce
 newly-supported platforms. Previous recipes in the release are refreshed
 and supported for at least one additional Yocto Project release. As they
 align, these previous releases are updated to include the latest from

documentation/kernel-dev/kernel-dev-maint-appx.rst

@@ -10,7 +10,7 @@ Tree Construction
 This section describes construction of the Yocto Project kernel source
 repositories as accomplished by the Yocto Project team to create Yocto
 Linux kernel repositories. These kernel repositories are found under the
-heading "Yocto Linux Kernel" at `YOCTO_GIT_URL <&YOCTO_GIT_URL;>`__ and
+heading "Yocto Linux Kernel" at :yocto_git:`/` and
 are shipped as part of a Yocto Project release. The team creates these
 repositories by compiling and executing the set of feature descriptions
 for every BSP and feature in the product. Those feature descriptions
@@ -80,7 +80,7 @@ to the kernel.
 
 The following steps describe what happens when the Yocto Project Team
 constructs the Yocto Project kernel source Git repository (or tree)
-found at ` <&YOCTO_GIT_URL;>`__ given the introduction of a new
+found at :yocto_git:`/` given the introduction of a new
 top-level kernel feature or BSP. The following actions effectively
 provide the Metadata and create the tree that includes the new feature,
 patch, or BSP:
@@ -93,10 +93,9 @@ patch, or BSP:
    located by searching these system directories:
 
    -  The in-tree kernel-cache directories, which are located in the
-      ```yocto-kernel-cache`` <&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache/tree/bsp>`__
+      :yocto_git:`yocto-kernel-cache </cgit/cgit.cgi/yocto-kernel-cache/tree/bsp>`
       repository organized under the "Yocto Linux Kernel" heading in the
-      `Yocto Project Source
-      Repositories <http://git.yoctoproject.org/cgit/cgit.cgi>`__.
+      :yocto_git:`Yocto Project Source Repositories <>`.
 
    -  Areas pointed to by ``SRC_URI`` statements found in kernel recipes
 
@@ -143,8 +142,7 @@ specific to some target hardware.
       as shipped with the Yocto Project release. Any add-ons and
       configuration data are applied to the end of an existing branch.
       The full repository generation that is found in the official Yocto
-      Project kernel repositories at
-      `http://git.yoctoproject.org <&YOCTO_GIT_URL;>`__ is the
+      Project kernel repositories at :yocto_git:`/` is the
       combination of all supported boards and configurations.
 
    -  The technique the Yocto Project team uses is flexible and allows
@@ -152,12 +150,12 @@ specific to some target hardware.
       patches specific to a deployment. Any additions to the kernel
       become an integrated part of the branches.
 
-   -  The full kernel tree that you see on ` <&YOCTO_GIT_URL;>`__ is
+   -  The full kernel tree that you see on :yocto_git:`/` is
       generated through repeating the above steps for all valid BSPs.
       The end result is a branched, clean history tree that makes up the
       kernel for a given release. You can see the script (``kgit-scc``)
       responsible for this in the
-      ```yocto-kernel-tools`` <&YOCTO_GIT_URL;/cgit.cgi/yocto-kernel-tools/tree/tools>`__
+      :yocto_git:`yocto-kernel-tools </cgit.cgi/yocto-kernel-tools/tree/tools>`
       repository.
 
    -  The steps used to construct the full kernel tree are the same