Review this information about out-of-place upgrade of Oracle Grid Infrastructure.
With an out-of-place upgrade, the installer installs the newer version in a separate Oracle Clusterware home. Both versions of Oracle Clusterware are on each cluster member node, but only one version is active.
Rolling upgrade avoids downtime and ensure continuous availability while the software is upgraded to a new version.
If you have separate Oracle Clusterware homes on each node, then you can perform an out-of-place upgrade on all nodes, or perform an out-of-place rolling upgrade, so that some nodes are running Oracle Clusterware from the earlier version Oracle Clusterware home, and other nodes are running Oracle Clusterware from the new Oracle Clusterware home.
An in-place upgrade of Oracle Grid Infrastructure is not supported.