[media] v4l: Add M420 format definition

M420 is a hybrid YUV 4:2:0 packet/planar format. Two Y lines are
followed by an interleaved U/V line.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[laurent.pinchart@ideasonboard.com: split into v4l/uvcvideo patches]
[laurent.pinchart@ideasonboard.com: add documentation]
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index a417270..8a4c309 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -336,6 +336,7 @@
 #define V4L2_PIX_FMT_YUV420  v4l2_fourcc('Y', 'U', '1', '2') /* 12  YUV 4:2:0     */
 #define V4L2_PIX_FMT_HI240   v4l2_fourcc('H', 'I', '2', '4') /*  8  8-bit color   */
 #define V4L2_PIX_FMT_HM12    v4l2_fourcc('H', 'M', '1', '2') /*  8  YUV 4:2:0 16x16 macroblocks */
+#define V4L2_PIX_FMT_M420    v4l2_fourcc('M', '4', '2', '0') /* 12  YUV 4:2:0 2 lines y, 1 line uv interleaved */
 
 /* two planes -- one Y, one Cr + Cb interleaved  */
 #define V4L2_PIX_FMT_NV12    v4l2_fourcc('N', 'V', '1', '2') /* 12  Y/CbCr 4:2:0  */