Docs: Add res. overlay info, update circ icons. Test: make online-sac-docs on instance #23 Bug: 32256871 Change-Id: I1457ef7625f1e783e2677d5430e1ad3b9714e729

diff --git a/src/devices/tech/display/circular-icons.jd b/src/devices/tech/display/circular-icons.jd
index f429e6e..30ac1dc 100644
--- a/src/devices/tech/display/circular-icons.jd
+++ b/src/devices/tech/display/circular-icons.jd

@@ -18,17 +18,19 @@
 -->
 
 <p>Circular <a
-href="https://developer.android.com/guide/practices/ui_guidelines/icon_design_launcher.html">launcher
-icons</a> are supported in Android 7.1.1 and later. Circular launcher icons are not
-enabled by default. To use circular icons in your device implementation, you
-must edit the resource overlay on your device to enable them.</p>
+  href="https://developer.android.com/guide/practices/ui_guidelines/icon_design_launcher.html">launcher
+  icons</a> are supported in Android 7.1.1 and later. Circular launcher icons
+are not enabled by default. To use circular icons in your device
+implementation, you must edit the <a
+  href="{@docRoot}source/add-device.html#use-resource-overlays">resource
+  overlay</a> on your device to enable them.</p>
 
-<p>The resource overlay file is at:
+<p>The resource file you are using an overlay on is at:
 <code><a
-href="https://android.googlesource.com/platform/frameworks/base/+/master/core/res/res/values/config.xml">/android/frameworks/base/core/res/res/values/config.xml</a></code>
+href="https://android.googlesource.com/platform/frameworks/base/+/master/core/res/res/values/config.xml">frameworks/base/core/res/res/values/config.xml</a></code>
 
 <p>To enable circular icons, change the <code>config_useRoundIcon</code>
-setting, shown below, from <code>false</code> to <code>true</code>:</p>
+setting in your overlay file from <code>false</code> to <code>true</code>:</p>
 
 <pre>
 &lt;!-- Flag indicating whether round icons should be parsed from the application manifest. --&gt;

diff --git a/src/source/add-device.jd b/src/source/add-device.jd
index 8dd5c6b..11ff829 100644
--- a/src/source/add-device.jd
+++ b/src/source/add-device.jd

@@ -133,6 +133,40 @@
 </tr>
 </table>
 
+<h2 id="use-resource-overlays">Customize the Build with Resource Overlays</h2>
+
+<p>The Android build system uses resource overlays to customize
+a product at build time. Resource overlays specify resource
+files that are applied on top of the defaults. To use resource overlays, modify the project
+buildfile to set <code>PRODUCT_PACKAGE_OVERLAYS</code> to a
+path relative to your top-level directory. That path becomes a shadow root searched along with
+the current root  when the build system searches for resources.</p>
+
+<p>The most commonly customized settings are contained in the file <a
+href="https://android.googlesource.com/platform/frameworks/base/+/master/core/res/res/values/config.xml">frameworks/base/core/res/res/config.xml</a>.</p>
+
+<p> To set up a resource overlay on this file, add the overlay directory to the
+project buildfile, as follows:</p>
+
+<pre>
+PRODUCT_PACKAGE_OVERLAYS := device/<i>device_implementer</i>/<i>device_name</i>/overlay
+</pre>
+
+<p>or</p>
+
+<pre>
+PRODUCT_PACKAGE_OVERLAYS := vendor/<i>vendor_name</i>/overlay
+</pre>
+
+<p> Then, add an overlay file to the directory, for example:</p>
+
+<pre>
+vendor/foobar/overlay/frameworks/base/core/res/res/config.xml
+</pre>
+
+<p> Any strings or string arrays found in the overlay <code>config.xml</code> file replace
+those found in the original file.</p>
+
 <h2 id="build-a-product">Build a Product</h2>
 
 <p>