[media] doc: v4l: add documentation for selection API

This patch adds a documentation for VIDIOC_{G/S}_SELECTION ioctl. Moreover, the
patch adds the description of modeling of composing, cropping and scaling
features in V4L2. Finally, some examples are presented.
Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/v4l/common.xml

@@ -1168,6 +1168,8 @@ dheight = format.fmt.pix.height;
     </section>
   </section>
 
+  &sub-selection-api;
+
   <section id="streaming-par">
     <title>Streaming Parameters</title>
 

Documentation/DocBook/media/v4l/compat.xml

@@ -2376,6 +2376,12 @@ that used it. It was originally scheduled for removal in 2.6.35.
         <listitem>
 	  <para>V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to userspace.</para>
         </listitem>
+        <listitem>
+	  <para>Add selection API for extended control over cropping and
+composing. Does not affect the compatibility of current drivers and
+applications.  See <link linkend="selection-api"> selection API </link> for
+details.</para>
+        </listitem>
       </orderedlist>
     </section>
 
@@ -2500,6 +2506,9 @@ ioctls.</para>
         <listitem>
 	  <para>&VIDIOC-CREATE-BUFS; and &VIDIOC-PREPARE-BUF; ioctls.</para>
         </listitem>
+        <listitem>
+	  <para>Selection API. <xref linkend="selection-api" /></para>
+        </listitem>
       </itemizedlist>
     </section>
 

Documentation/DocBook/media/v4l/v4l2.xml

@@ -501,6 +501,7 @@ and discussions on the V4L mailing list.</revremark>
     &sub-g-output;
     &sub-g-parm;
     &sub-g-priority;
+    &sub-g-selection;
     &sub-g-sliced-vbi-cap;
     &sub-g-std;
     &sub-g-tuner;