Rolling Upgrade in 12c - need for license clarification

Hi,

I'm currently planing a 12c project. So I have to compare the features by editions to result in decide if we use Oracle Standard or EE.

I found out that "Rolling Upgrades—Patch Set, Database, and Operating System"-feature is only in EE available.

Does that mean, that you will need the EE for a rolling upgrade with a regulary PSU (opatch apply -local) of RAC, performing that node by node, too. 

Or is that for major relase upgrades (e.g. 12.1.0.1=>12.1.0.2) needed only?

I did not found a sound doc, which can me answer that.

Thank you, Peter