buildroot/board/raspberrypi/post-image.sh

#!/bin/sh

BOARD_DIR="$(dirname $0)"
BOARD_NAME="$(basename ${BOARD_DIR})"
GENIMAGE_CFG="${BOARD_DIR}/genimage-${BOARD_NAME}.cfg"
GENIMAGE_TMP="${BUILD_DIR}/genimage.tmp"

case "${2}" in
	--add-pi3-miniuart-bt-overlay)
	if ! grep -qE '^dtoverlay=' "${BINARIES_DIR}/rpi-firmware/config.txt"; then
		echo "Adding 'dtoverlay=pi3-miniuart-bt' to config.txt (fixes ttyAMA0 serial console)."
		cat << __EOF__ >> "${BINARIES_DIR}/rpi-firmware/config.txt"

# fixes rpi3 ttyAMA0 serial console
dtoverlay=pi3-miniuart-bt
__EOF__
	fi
	;;
esac

rm -rf "${GENIMAGE_TMP}"

genimage                           \
	--rootpath "${TARGET_DIR}"     \
	--tmppath "${GENIMAGE_TMP}"    \
	--inputpath "${BINARIES_DIR}"  \
	--outputpath "${BINARIES_DIR}" \
	--config "${GENIMAGE_CFG}"

exit $?