Where should "standard FDT overlay files" go?

[Jason Thorpe <thorpej%me.com@localhost>]

Hey folks --

So, I have a little expansion board for my Orange Pi Zero Plus that Xunlong sells on the AliExpress store that has a USB->SATA interface, a SATA HDD connector, and an M2 SATA slot.  It's designed to mate update up with the Orange Pi Zero and Zero Plus using the 13-pin header.  (You can supply the Orange Pi Zero's +5V power rail from this board as well.)

To use it, you need to enable the ohci2/ehci2 USB interface on the Zero / Zero Plus board, which is disabled by default.

FDT overlay to the rescue.

Now, because this is an off-the-shelf thing you can buy, it seems useful to include it with the system as an overlay that you can simply enable by adding it to your efiboot.plist file (now you know why I added FDT overlay support too efiboot :-)

My thought was to add an "overlays" subdirectory to src/sys/arch/arm/dts, and have a build pass generate the .dtbo file, and then install them in a new standard system location: /stand/evbarm/dtb.  On Zero Plus, I currently have:

opi-zero-plus:thorpej 54$ ls -ll /stand/evbarm/dtb/sunxi-h3-h5-orangepi-zero-n 
8 -rw-r--r--  1 root  wheel  393 Apr 20 15:41 /stand/evbarm/dtb/sunxi-h3-h5-orangepi-zero-nas.dtbo
opi-zero-plus:thorpej 55$ 

...and my /etc/efiboot.plist file has:

opi-zero-plus:thorpej 55$ cat /etc/efiboot.plist                               
<plist>
<dict>
        <key>device-tree-overlays</key>
        <array>
                <string>/stand/evbarm/dtb/sunxi-h3-h5-orangepi-zero-nas.dtbo</string>
        </array>
</dict>
</plist>
opi-zero-plus:thorpej 56$ 

Anyone have any other thoughts on where these types of files should go?

-- thorpej