Build buildroot rootfs:
Enter into buildroot working directory
Compile the rootfs,Generate the rootfs in buildroot/output/images directory.
make rockchip_rk3399_defconfig make
You can use following integrative cmds and scripts to build firmware:
cd buildroot && make rockchip_rk3399_defconfig && cd .. && ./build_all.sh && ./mkfirmware.sh
Generate the firmware in rockimg directory.
In order to get more details,you could refer to <RK3399 Linux Buildroot System Development Guide.pdf> in docs directory.