There is support for mx25 in the mainline kernel:
arch/arm/mach-imx/mach-mx25_3ds.c
and also device tree support (very basic):
arch/arm/boot/dts/imx25-pdk.dts
I suggest you to look at the other mx25 boards in the dts directory in linux-next git tree, as there have been some recent patches for adding device tree support to mx25.
Regards,
Fabio Estevam