linux-yocto custom device tree in overlay

[Andreas Galauner <andreas@galauner.de>]

Hi Yocto Community,

I'm currently trying to build a custom image for a beaglebone black for
which I need to enable the can-controllers on the SoC. I managed to
create an overlay which already deals with building a few tools for CAN
communication, I created a kernel config snippet for linux-yocto to
enable CAN-support in the kernel and it already works with a USB
transceiver.

Now I need to modify the device tree for the board to enable the SoC
controllers. How do I put the device tree into my overlay? I tried
several ways, but the kernel buildsystem doesn't seem to find the dts
file to be compiled.

That definitely doesn't work:
> SRC_URI += "file://can.cfg \
>             file://am335x-boneblack-cansniff.dts"
> KERNEL_DEVICETREE = "am335x-boneblack-cansniff.dtb"

Any ideas? Google wasn't too fruitful either.
With non-yocto kernels I always put the device tree into the whole path
like 'git/arch/arm/boot/dts/mydevicetree.dts'  but that also doesn't
seem to work on linux-yocto because it uses another layout in its
working directory.

I'd rather not want to create my own git repo for linux-yocto like I did
for another project where I needed the same.

Thanks for your help,
- Andy