For over one year there's been an open-source Exynos DRM driver that made it into the mainline Linux kernel. The Exynos DRM doesn't support handling any accelerated 3D or video playback as it just covers their display controller and not the Mali GPU, but it's in fairly good shape these days and Samsung developers continue improving it for nearly every major kernel release.
They have made several improvements to their open-source Linux graphics driver in recent releases and there will be more to see with the Linux 3.8 kernel.
Inki Dae of Samsung has sent in a second pull request to David Airlie that integrates more Samsung Exynos DRM code for the drm-next repository that will be merged in Linux 3.8.
This second pull adds support for sending AVI and AVI info frames, a bug-fix for the previous pull, and various code clean-ups. The earlier pre-3.8 pull added in IOMMU support, a userptr feature to G2D, and minor fixes.
Still to be pulled are patches waiting for review that add in an IPP subsystem, run-time power management support for the HDMI and mixer components, and possibly additional fixes/clean-ups. The Exynos IPP subsystem is for Image Post Processing and supports image scalar/rotator/crop/flip/color-space and input/output operations.
This second Exynos 3.8 pull request can be found on the DRI mailing list.