In the devices I've looked at, append-dtb or KERNEL_DTB are used in the target makefile:
The dtb is built from here:
The build process for my devices compiles the dts files to here: ls build_dir/target-*/linux-*/*.dt*
On a device which uses dts, you can normally see the device tree here (but this can be configured off): ls /proc/device-tree/ hexdump -C /proc/device-tree/compatible