Booting Yggdrasil OS on Starfive VisionFive 2 RISC-V board:

* TODO: proper format for initrd image
* TODO: 0x70000000 can be replaced with a builtin var?

Prerequisites:

* OpenSBI + u-boot (you can use the regular debian installation from Starfive)
* yggdrasil-kernel.bin
* initrd.img

Steps:

1. Copy yggdrasil-kernel.bin and initrd.img into some directory and start a TFTP server there
2. Connect to VF2's serial port, ethernet and enter u-boot
3. Run the following commands:

# Get an IP address
dhcp
# [Optional] set some kernel cmdline params
setenv bootargs "debug.serial-level=info"
# Load initrd
tftpboot 0x70000000 <your-ip-address>:initrd.img
# Load kernel
tftpboot ${loadaddr} <your-ip-address>:yggdrasil-kernel.bin
# Load dtb
load mmc 1:3 ${fdt_addr_r} dtbs/...-starfive/starfive/${fdtfile}
fdt resize
# Enter the kernel
booti ${loadaddr} 0x70000000:<initrd-size> ${fdt_addr_r}