Working with patches in the build system

make target/linux/{clean,prepare} QUILT=1
cd build_dir/target-arm_cortex-a9_musl_eabi/linux-bcm53xx_generic/linux-5.4.117/
quilt new platform/020-ARM-BCM5301X-Add-DT-for-ASUS-RT-AC88U.patch
quilt edit arch/arm/boot/dts/Makefile
quilt add arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts
quilt refresh
cd ../../../../
make target/linux/update package/index V=s
make target/linux/{clean,compile} V=s

Edit a patch

make target/linux/{clean,prepare} QUILT=1
cd build_dir/target-arm_cortex-a9_musl_eabi/linux-bcm53xx_generic/linux-5.4.117/
quilt series
quilt push platform/305-ARM-BCM5301X-Add-DT-for-Asus-RT-AC88U.patch
quilt edit arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts (nano --syntax=css arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts)
quilt refresh
cd ../../../../
make target/linux/update package/index V=s

Easy Edit

make target/linux/{clean,prepare} QUILT=1 && cd build_dir/target-arm_cortex-a9_musl_eabi/linux-bcm53xx_generic/linux-5.10.61/ && quilt push platform/305-ARM-BCM5301X-Add-DT-for-Asus-RT-AC88U.patch && nano --syntax=css arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts
quilt refresh && cd ../../../../ && make target/linux/update package/index