[media] DocBook: document when to return ENODATA

ENODATA should be returned if the API used for getting, changing, querying
or enumerating the current video timings is not supported by the current input
or output.
This was decided during the 2012 Media Workshop.

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/vidioc-querystd.xml b/Documentation/DocBook/media/v4l/vidioc-querystd.xml
index 4b79c7c..fe80a18 100644
--- a/Documentation/DocBook/media/v4l/vidioc-querystd.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-querystd.xml
@@ -62,5 +62,13 @@
 
   <refsect1>
     &return-value;
+    <variablelist>
+      <varlistentry>
+	<term><errorcode>ENODATA</errorcode></term>
+	<listitem>
+	  <para>Standard video timings are not supported for this input or output.</para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
   </refsect1>
 </refentry>