Trying to find doc or figure out if there is a recommended order of operation for rebooting secondary instance in always on when in synchronous commit mode.

Since the primary replica waits on the secondary to commit changes, should we suspend data movement to avoid issues while rebooting the secondary replica?

using 2 replicas 2012 sp 1.  There are a few bugs with sp1 which makes me cautious about this.

I admit that I am long passed SQL 2012, but in our environment (SQL2014 SP1) we do nothing special, we just reboot. When the reboot is clean (="normal" system shutdown) the secondary will send a signal to the primary during shutdown so no waits will occur. Only if you are unclean in the shutdown (=BSOD) you will see delays.

One more thing to consider: If you do suspend data movement (which I would not!) you have to ensure that no log backups are taken anymore, otherwise you can't resume data movement after the reboot of the secondary. But that's only IF you suspend data movement.