Add device tree overlay support in Linux, U-Boot, and post image script

board/raspberrypi/post-image.sh

@@ -20,6 +20,10 @@ if [ ! -e "${GENIMAGE_CFG}" ]; then
 		FILES+=( "${i#${BINARIES_DIR}/}" )
 	done
 
+	for i in "${BINARIES_DIR}"/*.dtbo; do
+		FILES+=( "${i#${BINARIES_DIR}/}" )
+	done
+
 	FILES+=( "u-boot.bin" )
 	FILES+=( "zImage" )
 	FILES+=( "extlinux/" )

board/raspberrypi/uboot-patches/0001-rpi-add-fdtoverlay_addr_r-to-support-DT-overlays.patch

@@ -0,0 +1,10 @@
+--- a/board/raspberrypi/rpi/rpi.env
++++ b/board/raspberrypi/rpi/rpi.env
+@@ -75,6 +75,7 @@
+ scriptaddr=0x05400000
+ pxefile_addr_r=0x05500000
+ fdt_addr_r=0x05600000
++fdtoverlay_addr_r=0x056A0000
+ ramdisk_addr_r=0x05700000
+ 
+ boot_targets=mmc usb pxe dhcp