lua loader

I’ve been looking through the lua code in /boot/loader/lua I can’t really say I understand how the FDT gets loaded or even find the code that does but I am able to load a DTB using:

load -t dtb /boot/dtb/foo.dtb

It doesn’t see that overlays are supported (at least in the lua loader).  I have a fdt_overlay=“overlay.dtb” statement in my loader.conf but I don’t see it being honored.
Am I correct in understanding that?

If I’m not correct could someone point me at the code that does the overlay loading so I could look at it?
Thanks
Christopher