recipe for target 'dtbs' failed make: *** [dtbs] Error 2

Im trying to modify the pinmux to utilise PWM.

I followed the pdf and this command

make ARCH=arm64 dtbs

generates that error

Please refer to the whole steps in “Building the NVIDIA Kernel”

https://docs.nvidia.com/jetson/l4t/index.html#page/Tegra%2520Linux%2520Driver%2520Package%2520Development%2520Guide%2Fkernel_custom.html