[media] v4l: Create v4l2 subdev file handle structure

Used for storing subdev information per file handle and hold V4L2 file
handle.

Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Antti Koskipaa <akoskipa@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/Kconfig b/drivers/media/Kconfig
index 2466f2b..6995940 100644
--- a/drivers/media/Kconfig
+++ b/drivers/media/Kconfig
@@ -53,6 +53,15 @@
 	depends on (I2C || I2C=n) && VIDEO_DEV
 	default (I2C || I2C=n) && VIDEO_DEV
 
+config VIDEO_V4L2_SUBDEV_API
+	bool "V4L2 sub-device userspace API (EXPERIMENTAL)"
+	depends on VIDEO_DEV && MEDIA_CONTROLLER && EXPERIMENTAL
+	---help---
+	  Enables the V4L2 sub-device pad-level userspace API used to configure
+	  video format, size and frame rate between hardware blocks.
+
+	  This API is mostly used by camera interfaces in embedded platforms.
+
 #
 # DVB Core
 #