Hi there,
from what I understand from your post you want FOG to be able to get the MAC address of the IPMI interface and add it to the inventory.
From what I know about the supermicro IPMI would not be possible without integrating some form of IPMI driver into the linux kernel FOG boots to gather this inventory.
The actual machine doesn’t see the IPMI as a network card as such, only a device in device manager (if it was windows)
When the kernel boots and gathers its inventory you might be able to get some information from dmidecode once said driver is installed but I imagine it would be limited information as its meant to go the other way ie get information about the system while logged in via IPMI interface, not the other way which could also be a security risk.
let us know how you get on as I have thought about this same issue with HP iLO before and could be handy to have a link to the IPMI/iLO from inside FOG inventory