ref-manual: add "Mixin" term

Also add a target (and use) a target
for the "Long Term Support Release" section.

(From yocto-docs rev: 98d6f2066fcdb20e63b8da6ed52d0f3590b15195)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/release-process.rst

@@ -87,6 +87,8 @@ stable release.
    exception to this policy occurs when there is a strong reason such as
    the fix happens to also be the preferred upstream approach.
 
+.. _ref-long-term-support-releases:
+
 Long Term Support Releases
 ==========================
 
@@ -120,16 +122,16 @@ of stable and :term:`LTS` releases.
 
    In some circumstances, a layer can be created by the community in order to
    add a specific feature or support a new version of some package for an :term:`LTS`
-   release.  This is called a "mixin" layer. These are thin and specific
+   release.  This is called a :term:`Mixin` layer. These are thin and specific
    purpose layers which can be stacked with an :term:`LTS` release to "mix" a specific
    feature into that build. These are created on an as-needed basis and
    maintained by the people who need them.
 
    Policies on testing these layers depend on how widespread their usage is and
-   determined on a case-by-case basis. You can find some "mixin" layers in the
+   determined on a case-by-case basis. You can find some :term:`Mixin` layers in the
    :yocto_git:`meta-lts-mixins </meta-lts-mixins>` repository. While the Yocto
    Project provides hosting for those repositories, it does not provides
-   testing on them. Other "mixin" layers may be released elsewhere by the wider
+   testing on them. Other :term:`Mixin` layers may be released elsewhere by the wider
    community.
 
 Testing and Quality Assurance

documentation/ref-manual/terms.rst

@@ -277,7 +277,7 @@ universal, the list includes them just in case:
       This term means "Long Term Support", and in the context of the Yocto
       Project, it corresponds to selected stable releases for which bug and
       security fixes are provided for at least two years. See
-      ":doc:`/ref-manual/release-process`" for details.
+      the :ref:`ref-long-term-support-releases` section for details.
 
    :term:`Metadata`
       A key element of the Yocto Project is the Metadata that
@@ -298,6 +298,12 @@ universal, the list includes them just in case:
       :yocto_git:`yocto-kernel-cache </yocto-kernel-cache>`
       Git repository.
 
+   :term:`Mixin`
+      A :term:`Mixin` layer is a layer which can be created by the community to
+      add a specific feature or support a new version of some package for an
+      :term:`LTS` release. See the :ref:`ref-long-term-support-releases`
+      section for details.
+
    :term:`OpenEmbedded-Core (OE-Core)`
       OE-Core is metadata comprised of
       foundational recipes, classes, and associated files that are meant to