Compile EDK2 to set boot order to PXE



I am network booting the raspberry pi firmware. Unfortunately as its loaded from TFTP it does not retain settings nor do I believe I can give it settings.
I am already compiling my own version of RPi4 uefi with edk-platforms/../Rpi4/.dsc edited for some better defaults like setting higher memory.
However, I can't find an option to force a particular boot option as a default. Right now it tries to boot an .efi locally but that efi is not able to be found because we are booting from TFTP.
Instead I would like it to boot to PXE again where I can boot iPXE and control the boot process further. The end goal here is that I can boot UEFI -> iPXE without an SD card.

Could you help me find out what option/variable I can set in the platform dsc? I think the option should be in MdePkg.dec but I can't find any "DefaultBootOption" or override variable.

Kind regards,

Werner Buck

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