I committed the v4l2 support into the linuxulator (in 9–current). Part of this was the import of the v4l2 header from linux. We have the permission to use it (like the v4l one), it is not licensed via GPL. This means we can use it in FreeBSD native drivers, and they are even allowed to be compiled into GENERIC (but I doubt we have a driver which could provide the v4l2 interface in GENERIC).
Thanks to nox@ for writing the glue code.