[Buildroot] [git commit] package/rpi-firmware: add overlays/README

[Thomas Petazzoni]

commit: https://git.buildroot.net/buildroot/commit/?id=558946676958ed471d5c72867318a1b61b6e0e69
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/master

If a custom os_prefix directory is specified then the Raspberry Pi
firmware probes for the README file in overlays directory. If
this is not found then firmware will use the top-level overlays
directory which can be confusing if os_prefix is used in conjunction
with other filters to implement alternate boot behaviour.

In Raspberry Pi OS the README file is always included to ensure
that the relevant documentation is in sync with the overlays. Rather
that including the entire file let's just include an empty file so
that overlays directory is consistent with the Raspberry Pi OS
APT package.

From
https://www.raspberrypi.com/documentation/computers/config_txt.html#overlay_prefix

Unless ${os_prefix}${overlay_prefix}README exists, overlays are shared
with the main OS (i.e. os_prefix is ignored).

Signed-off-by: Tim Gover <tim.gover at raspberrypi.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
---
 package/rpi-firmware/rpi-firmware.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/package/rpi-firmware/rpi-firmware.mk b/package/rpi-firmware/rpi-firmware.mk
index 6f5902fd52..53d6d8ca06 100644
--- a/package/rpi-firmware/rpi-firmware.mk
+++ b/package/rpi-firmware/rpi-firmware.mk
@@ -57,6 +57,7 @@ define RPI_FIRMWARE_INSTALL_DTB_OVERLAYS
 		$(INSTALL) -D -m 0644 $(ovldtb) $(BINARIES_DIR)/rpi-firmware/overlays/$(notdir $(ovldtb))
 	)
 	$(INSTALL) -D -m 0644 $(@D)/boot/overlays/overlay_map.dtb $(BINARIES_DIR)/rpi-firmware/overlays/
+	touch $(BINARIES_DIR)/rpi-firmware/overlays/README
 endef
 else
 # Still create the directory, so a genimage.cfg can include it independently of