Best way to backup DRM and root Lollipop 5.1.1.?

Had to upgrade my Nexus 4 to an Xperia Z1c a while ago, and that **** was eeeaaasy as hell to root.
Now, is there a step by step tutorial on how to root 5.1.1. while KEEPING the DRM / backing it up? Dont wanna mess anything up here.