DRM Render Nodes are about allowing Linux DRM kernel drivers to support GPGPU/OpenCL compute support without an active display interface and basically breaking apart the mode-setting and rendering capabilities.
With this commit by Intel's Chris Wilson, "Render nodes allow clients full access to off-screen rendering and GPU offload, without assuming any master responsibilities (for device and display management). As they have a more limited interface, they can be used in a more permissive manner."
The kernel-side work for DRM Render Nodes will hopefully be merged into Linux 3.12 (or Linux 3.13) to make all of this work as part of a Google Summer of Code project a reality. David Herrmann has been the student developer spearheading the DRM render/mode-set nodes.