Serial over LAN for Mt. Collins BMC

I’m installing Ubuntu 22.04 and it installs and runs fine. The only problem is that the boot process is not shown on the screen. This can be worked around by add console=tty0 to the command line. This uses the framebuffer I believe.

By default, I think the kernel reads bootarg from the device tree and outputs the boot process via UART to one of the serial ports. However, I can’t see any output using Serial over LAN of the BMC.

So my questions are:

  1. Which /dev/tty* is the Serial over LAN port mapped to when the system is fully boot?
  2. Which parameters should be supplied to console or earlycon so that the boot process can be monitored using Serial over LAN.
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In case someone else has similar problems, the symptom is that the boot seems to stuck at EFI stub: Exiting boot services.... The boot process continues, and you will see the login screen after a while. To monitor the boot process via VGA, just add console=tty0 to the kernel command line.