How to build Openwrt for Beaglebone green wireless?

I'm a newbie trying to build Openwrt to run on a Beaglebone green wireless board.

When building for the bone black I can see that a .dtb file (am335x-bonegreen-wirelss.dtb) is generated which leads me to think that it should be possible, but I cannot see a way to select the board in menuconfig.

Can anyone give me some guidance on how I can build an image for this board?