I have tried using fstab to mount /dev/mmcblk0p10 on /overlay or on / during boot (pivot overlay and pivot root), but none of them succeed. They both mount back to /dev/loop0
It's possible to mount it by typing mount /dev/mmcblk0p10 /overlay, but like Kostja mentioned, this won't survive the reboot.
Any help or ideas will be appreciated.