Using Armbian build:
If creating a patch for u-boot, the dts will go in build/cache/sources/u-boot/v2022.07/arch/arm/dts/
Or similar depending on uboot version.
If creating a patch for kernel, the dts will go in build/cache/sources/linux-mainline/6.0/arch/arm64/boot/dts/rockchip/
Or similar depending on kernel version and architecture.
Don't forget to modify the Makefile's