I've been documenting my experience bringing up Debian with a v3.14
kernel here[1]. I've also documented how to modify the Devicetree as
well as build a new kernel. Let me know if anything needs clarification
or correction. Hopefully someone else finds it useful!
Cheers,
- Ben
[1] http://www.smart-cactus.org/~ben/posts/2014-09-12-bringing-up-debian-on-bbb.html
It looks good. But just realised i have to fix one little thing on the
"/uEnv.txt" -> "/boot/uEnv.txt" compatibilty for old eMMC u-boot's..
The "dtb=" will be ignored, as "/uEnv.txt" references it as "fdtfile"
so i need to add a quick if "dtb" defined use dtb value in /uEnv.txt
on the next snapshot next week.
So, if it's not doing what you want (you have an old bootloader in
eMMC) (and you don't want to update it)
use:
fdtfile=am335x-boneblack-mycape.dtb
too... till the dtb is fixed. 
Regards,