[media] v4l2: Add documentation for the FM RX controls

Add appropriate documentation for all the newly added standard
controls.
Based on the patch by Manjunatha Halli [1]
[1] http://lists-archives.com/linux-kernel/27641303-media-update-docs-for-v4l2-fm-new-features.html

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml
index 8c2b368..e44161f 100644
--- a/Documentation/DocBook/media/v4l/compat.xml
+++ b/Documentation/DocBook/media/v4l/compat.xml
@@ -2310,6 +2310,9 @@
 	<listitem>
 	  <para>Added FM Modulator (FM TX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_TX</constant> and their Control IDs.</para>
 	</listitem>
+<listitem>
+	  <para>Added FM Receiver (FM RX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_RX</constant> and their Control IDs.</para>
+	</listitem>
 	<listitem>
 	  <para>Added Remote Controller chapter, describing the default Remote Controller mapping for media devices.</para>
 	</listitem>