Split Brain scenario Always on Availability group

Due to maintenance our primary site will be offline for few hours. I have an availability group where there are 2 nodes at the primary site and one node at the DR Site. Since the Primary site will be off so I will need to failover to the DR site before the maintenance. My question is if I failover to the DR site and shut off all the nodes at the Primary site one after another and once the maintenance is over I simply turn back on the nodes at the primary server one by one and then failover to the primary site will that create a split brain scenario. Since the primary site will be down will the Windows server failover cluster go down and the availability group becomes inaccessible?