1. CRM为主设备 /dev/video0,先创建 v4l2_device 设备,再创建 video_device 设备,最后创建 media_device 设备/dev/media0
v4l2_device的mdev指向media_device,v4l2_device的entity链接到media_device的entities上(链表节点)
2. cpas为子设备 /dev/v4l2-subdev0,先创建 v4l2_subdev,v4l2_subdev的list指向v4l2_device的subdevs(链表节点)
v4l2_subdev的v4l2_dev指向v4l2_device,v4l2_subdev的entity链接到media_device的entities上(链表节点)
v4l2_subdev的devnode指向video_device用来创建节点/dev/v4l2-subdev0