[media] V4L2: Add per-device-node capabilities

If V4L2_CAP_DEVICE_CAPS is set, then the new device_caps field is filled with
the capabilities of the opened device node.

The capabilities field traditionally contains the capabilities of the physical
device, being a superset of all capabilities available at the several device
nodes. E.g., if you open /dev/video0, then if it contains VBI caps then that means
that there is a corresponding vbi node as well. And the capabilities field of
both the video and vbi nodes should contain identical caps.

However, it would be very useful to also have a capabilities field that contains
just the caps for the currently open device, hence the new CAP bit and field.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.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 c736380..c93298f 100644
--- a/Documentation/DocBook/media/v4l/compat.xml
+++ b/Documentation/DocBook/media/v4l/compat.xml
@@ -2393,6 +2393,10 @@
 	    to the <link linkend="control">User controls class</link>.
 	  </para>
         </listitem>
+        <listitem>
+	  <para>Added the device_caps field to struct v4l2_capabilities and added the new
+	  V4L2_CAP_DEVICE_CAPS capability.</para>
+        </listitem>
       </orderedlist>
     </section>