media: vimc: documentation for lens

Add documentation for vimc-lens.
Add a lens into the vimc topology graph.

Signed-off-by: Yunke Cao <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

Documentation/admin-guide/media/vimc.dot

···
 	n00000001 [label="{{} | Sensor A\n/dev/v4l-subdev0 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
 	n00000001:port0 -> n00000005:port0 [style=bold]
 	n00000001:port0 -> n0000000b [style=bold]
+	n00000001 -> n00000002
+	n00000002 [label="{{} | Lens A\n/dev/v4l-subdev5 | {<port0>}}", shape=Mrecord, style=filled, fillcolor=green]
 	n00000003 [label="{{} | Sensor B\n/dev/v4l-subdev1 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
 	n00000003:port0 -> n00000008:port0 [style=bold]
 	n00000003:port0 -> n0000000f [style=bold]
+	n00000003 -> n00000004
+	n00000004 [label="{{} | Lens B\n/dev/v4l-subdev6 | {<port0>}}", shape=Mrecord, style=filled, fillcolor=green]
 	n00000005 [label="{{<port0> 0} | Debayer A\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
 	n00000005:port1 -> n00000015:port0
 	n00000008 [label="{{<port0> 0} | Debayer B\n/dev/v4l-subdev3 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]

Documentation/admin-guide/media/vimc.rst

···
 
 	* 1 Pad source
 
+vimc-lens:
+	Ancillary lens for a sensor. Supports auto focus control. Linked to
+	a vimc-sensor using an ancillary link. The lens supports FOCUS_ABSOLUTE
+	control.
+
+.. code-block:: bash
+
+	media-ctl -p
+	...
+	- entity 28: Lens A (0 pad, 0 link)
+			type V4L2 subdev subtype Lens flags 0
+			device node name /dev/v4l-subdev6
+	- entity 29: Lens B (0 pad, 0 link)
+			type V4L2 subdev subtype Lens flags 0
+			device node name /dev/v4l-subdev7
+	v4l2-ctl -d /dev/v4l-subdev7 -C focus_absolute
+	focus_absolute: 0
+
+
 vimc-debayer:
 	Transforms images in bayer format into a non-bayer format.
 	Exposes: