ref-manual: New section on Package Feeds.

Fixes [YOCTO #2808]

New section for package feeds created.  Includes a new figure
also.

(From yocto-docs rev: 6d8b41114ebadcfb06f6064a13c4da5b47a9f73c)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/technical-details.xml

@@ -744,6 +744,58 @@
             </para>
         </section>
     </section>
+
+    <section id="package-feeds-dev-environment">
+        <title>Package Feeds</title>
+
+        <para>
+            When the OpenEmbedded build system generates an image or an SDK,
+            it gets the packages from a package feed area located in the
+            <ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
+            The main
+            <link linkend='a-closer-look-at-the-yocto-project-development-environment'>Yocto Project Development Environment</link>
+            figure shows this package feeds area in the upper-right corner.
+        </para>
+
+        <para>
+            This section looks a little closer into the package feeds area used
+            by the build system.
+            Here is a more detailed look at the area:
+            <imagedata fileref="figures/package-feeds.png" align="center" width="7in" depth="6in" />
+        </para>
+
+        <para>
+            Package feeds are an intermediary step in the build process.
+            BitBake generates packages whose type is defined by the
+            <link linkend='var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></link>
+            variable.
+            Before placing the packages into package feeds,
+            the build process validates them with generated output quality
+            assurance checks through the
+            <link linkend='ref-classes-insane'><filename>insane.bbclass</filename></link>
+            class.
+        </para>
+
+        <para>
+            The package feed area resides in
+            <filename>tmp/deploy</filename> of the Build Directory.
+            Folders are created that correspond to the package type
+            (IPK, DEB, or RPM) created.
+            Further organization is derived through the value of the
+            <link linkend='var-PACKAGE_ARCH'><filename>PACKAGE_ARCH</filename></link>
+            variable for each package.
+            For example, packages can exist for the i586 or qemux86
+            architectures.
+            The package files themselves reside within the appropriate
+            architecture folder.
+        </para>
+
+        <para>
+            BitBake uses the <filename>do_package_write_*</filename> task to
+            place generated packages into the package holding area (e.g.
+            <filename>do_package_write_ipk</filename> for IPK packages).
+        </para>
+    </section>
 </section>
 
 <section id="cross-development-toolchain-generation">