sudo apt-get update
sudo apt-get install device-tree-compiler
Usually the dtb file used during the boot is saved on the microSD inside the directory /boot. In this example we will extract a dts file starting from the dtb file available on a RoadRunner board.
sudo dtc -I dtb -O dts -o acme-roadrunner.dts /boot/acme-roadrunner.dtb
Make your changes on the acme-roadrunner.dts file using an ASCII editor, copy your old copy of dtb file and generate the new dtb file by typing
cp /boot/acme-roadrunner.dtb /boot/acme-roadrunner-old.dtb
sudo dtc -I dts -O dtb -o /boot/acme-roadrunner.dtb acme-roadrunner.dts
Then reboot to test yor new device tree