It's been a long while since I did anything with UEFI, but my recollection is that the standard data structures are reasonably well documented, especially when they are meant to be part of booting an OS
I imagine that whatever UEFI extension implements loading a disk image over the network probably also implements some way of knowing where the sectors are in RAM so that the OS bootloader can choose to hand off access to the memory disk to the OS.
Is such support implemented in any bootloaders? I have no idea. My guess is probably not because people would rather just have the bootloader use the available services to download the disk image itself.
I imagine that whatever UEFI extension implements loading a disk image over the network probably also implements some way of knowing where the sectors are in RAM so that the OS bootloader can choose to hand off access to the memory disk to the OS.
Is such support implemented in any bootloaders? I have no idea. My guess is probably not because people would rather just have the bootloader use the available services to download the disk image itself.