Maybe some of these ideas will help?
https://bbs.archlinux.org/viewtopic.php?id=209121
https://aur.archlinux.org/packages/droidcam/
Apparently there is a group already working on a solution to access the camera from the android HAL and present it to Linux:
"provides a set of interfaces to libcamera for existing applications; they will include a V4L compatibility layer, an Android HAL interface, and a GStreamer interface. The intent is to make libcamera suitable for all Linux-based devices." https://lwn.net/Articles/794555/
https://libcamera.org/docs.html