After googling the errors,
I ended up trying this new command line:
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- deb-pkg
first errors are now gone,I wait for build result
I still have no idea of what to do next to take into account the dtb and the modules, and how to install all this on a running 4.9 or 4.12.7 system…
Edit:
build ended without error,
now, I see no evident sign of a .deb file anywhere, so, where is it ?