The basic, un-accelerated DRM driver in the Linux 3.2 kernel supports kernel mode-setting (KMS) on the Exynos 4210 SoC, which is found in products like the Samsung Galaxy S II. It's a good starting point and was accepted into the mainline tree since it doesn't expose any interfaces just for use by any Samsung binary blobs (i.e. closed-source user-space 3D support), but at the same time won't be of use to as many people without the 2D/3D hardware acceleration.
The latest work floating around by Samsung's Linux engineers unfortunately isn't for any acceleration support, but just completing other areas of the driver. Namely, there is now HDMI support available to the DRM driver (see this patch, among others). HDMI support was previously only available to on Exynos via a V4L2 driver.
What's still being worked on by the team of Linux driver developers at Samsung is DRM plane support, multi-planar format support for the video processor layer, sharing common low-level code with the V4L2 driver, and code cleaning.
Texas Instruments has also been working on an open-source ARM DRM driver for their OMAP SoCs.