sl/mnt OK, lukas.

U-Boot boot device (bootdev)

A bootdev provides a way to obtain a bootflow file from a device.  It is a
child of the media device (UCLASS_MMC, UCLASS_SPI_FLASH, etc.)

The bootdev driver is provided by the media devices.  The bindings for each
are described in this file (to come).

Required properties:

   "u-boot,bootdev-eth" - Ethernet bootdev
   "u-boot,bootdev-mmc" - MMC bootdev
   "u-boot,bootdev-usb" - USB bootdev


	mmc1 {
		compatible = "sandbox,mmc";

		mmc-bootdev {
			compatible = "u-boot,bootdev-eth";