Hi Bernhard
I added support for device trees in this commit: http://review.android.git.linaro.org/#change,1359
Is there any reason iMX6 can't make use of this rather than having a custom make recipe in tasks/kernel.mk? I believe that iMX6 just needs to add the following line to its BoardConfig.mk ...
DEVICE_TREES := imx6q-sabrelite:board.dtb