kumquat-buildroot/board/pc/genimage-efi.cfg

image efi-part.vfat {
  vfat {
    file startup.nsh {
      image = "efi-part/startup.nsh"
    }
    file EFI {
      image = "efi-part/EFI"
    }
    file bzImage {
      image = "bzImage"
    }
  }
  size = 16M
}

image disk.img {

  hdimage {
  }

  partition boot {
    partition-type = 0xEF
    image = "efi-part.vfat"
  }

  partition root {
    partition-type = 0x83
    image = "rootfs.ext2"
  }

}