In case anyone else is curious, DRM in the kernel stands for Direct Rendering Manager [1]. It has nothing to do with the DRM that's usually discussed on HN.
Considering the negative connotations of DRM, I am surprised it isn't named something else.
The name Direct Rendering Manager has been around since the '90s, since the XFree86 days. So I'm pretty sure this abbreviation predates that of the "bad" DRM.