sdk-manual: Updates to sections for updating installed Ext SDKs

There are two sections that deal with this topic.  One is from the
standpoint of a user using a 3rd party published and installed
extensible SDK ("Applying Updates to an Installed Extensible SDK").
The other is from the standpoint of a person providing Extensible
SDKs for consumption ("Providing Updates to the Extensible SDK
After Installation").  These sections needed some closer examination
regarding fully describing what was going on.  I provided some
re-writes to both.

(From yocto-docs rev: 1c60b13b5f1813d6e3688e1efce32b7f31422e86)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/sdk-manual/sdk-appendix-customizing.xml

@@ -213,12 +213,14 @@
     <para>
         When you make changes to your configuration or to the metadata and
         if you want those changes to be reflected in installed SDKs, you need
-        to perform additional steps to make it possible for those that use
-        the SDK to update their installations with the
+        to perform additional steps.
+        These steps make it possible for anyone using the installed SDKs to
+        update the installed SDKs by using the
         <filename>devtool sdk-update</filename> command:
         <orderedlist>
             <listitem><para>
                 Create a directory that can be shared over HTTP or HTTPS.
+                This directory will contain the published SDK.
                 </para></listitem>
             <listitem><para>
                 Set the
@@ -226,7 +228,10 @@
                 variable to point to the corresponding HTTP or HTTPS URL.
                 Setting this variable causes any SDK built to default to that
                 URL and thus, the user does not have to pass the URL to the
-                <filename>devtool sdk-update</filename> command.
+                <filename>devtool sdk-update</filename> command as described
+                in the
+                "<link linkend='sdk-applying-updates-to-an-installed-extensible-sdk'>Applying Updates to an Installed Extensible SDK</link>"
+                section.
                 </para></listitem>
             <listitem><para>
                 Build the extensible SDK normally (i.e., use the
@@ -236,7 +241,7 @@
             <listitem><para>
                 Publish the SDK using the following command:
                 <literallayout class='monospaced'>
-     $ oe-publish-sdk <replaceable>some_path</replaceable>/sdk-installer.sh <replaceable>path_to_shared/http_directory</replaceable>
+     $ oe-publish-sdk <replaceable>some_path</replaceable>/sdk-installer.sh <replaceable>path_to_shared_http_directory</replaceable>
                 </literallayout>
                 You must repeat this step each time you rebuild the SDK
                 with changes that you want to make available through the
@@ -246,11 +251,11 @@
     </para>
 
     <para>
-        Completing the above steps allows users of the existing SDKs to
-        simply run <filename>devtool sdk-update</filename> to retrieve the
-        latest updates.
+        Completing the above steps allows users of the existing installed
+        SDKs to simply run <filename>devtool sdk-update</filename> to
+        retrieve and apply the latest updates.
         See the
-        "<link linkend='sdk-updating-the-extensible-sdk'>Updating the Extensible SDK</link>"
+        "<link linkend='sdk-applying-updates-to-an-installed-extensible-sdk'>Applying Updates to an Installed Extensible SDK</link>"
         section for further information.
     </para>
 </section>

documentation/sdk-manual/sdk-extensible.xml

@@ -1715,31 +1715,35 @@
         </para>
     </section>
 
-    <section id='sdk-updating-the-extensible-sdk'>
-        <title>Updating the Extensible SDK</title>
+    <section id='sdk-applying-updates-to-an-installed-extensible-sdk'>
+        <title>Applying Updates to an Installed Extensible SDK</title>
 
         <para>
-            If you are working with an extensible SDK that gets occasionally
-            updated (e.g. typically when that SDK has been provided to you by
-            another party), then you will need to manually pull down those
-            updates to your installed SDK.
+            If you are working with an installed extensible SDK that gets
+            occasionally updated (e.g. a third-party SDK), then you will need
+            to manually "pull down" the updates into the installed SDK.
         </para>
 
         <para>
-            To update your installed SDK, run the following:
+            To update your installed SDK, use <filename>devtool</filename> as
+            follows:
             <literallayout class='monospaced'>
      $ devtool sdk-update
             </literallayout>
             The previous command assumes your SDK provider has set the default
-            update URL for you.
-            If that URL has not been set, you need to specify it yourself as
-            follows:
+            update URL for you through the
+            <ulink url='&YOCTO_DOCS_REF_URL;#var-SDK_UPDATE_URL'><filename>SDK_UPDATE_URL</filename></ulink>
+            variable as described in the
+            "<link linkend='sdk-providing-updates-to-the-extensible-sdk-after-installation'>Providing Updates to the Extensible SDK After Installation</link>"
+            section.
+            If the SDK provider has not set that default URL, you need to
+            specify it yourself in the command as follows:
             <literallayout class='monospaced'>
      $ devtool sdk-update <replaceable>path_to_update_directory</replaceable>
             </literallayout>
             <note>
-                The URL needs to point specifically to a published SDK and not an
-                SDK installer that you would download and install.
+                The URL needs to point specifically to a published SDK and
+                not to an SDK installer that you would download and install.
             </note>
         </para>
     </section>