Always On best practice for secondary node maintenance In my AG, I have two nodes using synchronous commit, automatic failover, allow all connections in primary role, and readable secondary as yes.  The failover cluster is using a fileshare witness as the quorum.  I have to reboot the secondary replica tonight.  

What is the best practice for handling this type of maintenance?  Since I have quorum, can I just reboot the secondary?  Do I need to drain roles of the secondary in the cluster manager?  Is there an AG maintenance mode?
No AG maintenance mode. You can restart secundary node and you will get events in logs, both SQL server and cluster, but nothing else. If you need to restart primary, first do an AG manual failover and check everything went fine.