Comment # 10 on bug 1205649 from Wenruo Qu

It is possible.

Since you can already mount the fs RO, you can go "btrfs subvolume list <mnt>"
to make sure which directory is subvolume 1628.

Another thing is, if you're using SUSE based distro, you may want to mount with
"-o rescue=all,ro,subvolid=5" to mount the real top level subvolume.
Or some subvolumes/snapshots may be hidden.

This can make a huge difference between the current /home is in-accessible from
some snapshots of /home are completely fine.