[media] V4L2: add a common V4L2 subdevice platform data type

This struct shall be used by subdevice drivers to pass per-subdevice data,
e.g. power supplies, to generic V4L2 methods, at the same time allowing
optional host-specific extensions via the host_priv pointer. To avoid
having to pass two pointers to those methods, add a pointer to this new
struct to struct v4l2_subdev.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

include/media/v4l2-subdev.h

@@ -559,6 +559,17 @@ struct v4l2_subdev_internal_ops {
 /* Set this flag if this subdev generates events. */
 #define V4L2_SUBDEV_FL_HAS_EVENTS		(1U << 3)
 
+struct regulator_bulk_data;
+
+struct v4l2_subdev_platform_data {
+	/* Optional regulators uset to power on/off the subdevice */
+	struct regulator_bulk_data *regulators;
+	int num_regulators;
+
+	/* Per-subdevice data, specific for a certain video host device */
+	void *host_priv;
+};
+
 /* Each instance of a subdev driver should create this struct, either
    stand-alone or embedded in a larger struct.
  */
@@ -592,6 +603,8 @@ struct v4l2_subdev {
 	struct v4l2_async_subdev *asd;
 	/* Pointer to the managing notifier. */
 	struct v4l2_async_notifier *notifier;
+	/* common part of subdevice platform data */
+	struct v4l2_subdev_platform_data *pdata;
 };
 
 #define media_entity_to_v4l2_subdev(ent) \