Restarting a cluster node is as simple as shutting down and restarting standard mysql. The node should gracefully leave the cluster (and the total vote count for quorum should decrement). When it rejoins, the node should receive an IST of changes since it left so it can get back in sync. If the set of changes needed for IST are not found in the gcache file on any other node in the entire cluster, then an SST will be performed instead. Therefore, restarting cluster nodes for rolling configuration changes or software upgrades should be fairly trivial to accomplish from the cluster’s perspective.
If a configuration change is done and mysql restarted and that change happens to contain a misspelling or some other mistake that prevents mysqld from loading, Galera will generally decide to drop its state and an SST will be forced for that node.