I have moved to running the vanilla mainline linux-3.11-rcN kernel on my Samsung Chromebook. There are some notes on the steps that I used to get it running at:
http://people.redhat.com/wcohen/chromebook/booting-3.11kernel.txt
The config file is a bit different than the fc20 kernel configuration. I started from the "make exynos_defconfig" and working towards something that is closer to the fc20 configuration. There are a couple drawbacks with this configuration. The usb3 and wireless are not working in the configuration. Also cool things like KVM virtualization are not working.
I was hoping to get the kernel to configure to support multiple ARM processors, but it looks like some patches will be needed to allow the ARCH_EXYNOS to be selected with ARCH_MULTI. Right now it looks like they are exclusive. The ARCH_EXYNOS also selects NEED_MACH_MEMORY_H which looks like there might be some arch specific includes as a result.
-Will