[media] media: add support for decoder as one of media entity types

A lot of SOCs including Texas Instruments Davinci family mainly use
video decoders as input devices. This patch adds a flag
'MEDIA_ENT_T_V4L2_SUBDEV_DECODER' media entity type for decoder's.
Along side updates the documentation for this media entity type.

Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/v4l/media-ioc-enum-entities.xml

@@ -272,6 +272,16 @@
 	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_LENS</constant></entry>
 	    <entry>Lens controller</entry>
 	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_DECODER</constant></entry>
+	    <entry>Video decoder, the basic function of the video decoder is to
+	    accept analogue video from a wide variety of sources such as
+	    broadcast, DVD players, cameras and video cassette recorders, in
+	    either NTSC, PAL or HD format and still occasionally SECAM, separate
+	    it into its component parts, luminance and chrominance, and output
+	    it in some digital video standard, with appropriate embedded timing
+	    signals.</entry>
+	  </row>
 	</tbody>
       </tgroup>
     </table>

include/uapi/linux/media.h

@@ -56,6 +56,8 @@ struct media_device_info {
 #define MEDIA_ENT_T_V4L2_SUBDEV_SENSOR	(MEDIA_ENT_T_V4L2_SUBDEV + 1)
 #define MEDIA_ENT_T_V4L2_SUBDEV_FLASH	(MEDIA_ENT_T_V4L2_SUBDEV + 2)
 #define MEDIA_ENT_T_V4L2_SUBDEV_LENS	(MEDIA_ENT_T_V4L2_SUBDEV + 3)
+/* A converter of analogue video to its digital representation. */
+#define MEDIA_ENT_T_V4L2_SUBDEV_DECODER	(MEDIA_ENT_T_V4L2_SUBDEV + 4)
 
 #define MEDIA_ENT_FL_DEFAULT		(1 << 0)