Do refer to the AppleTalk chapter in Inside Macintosh volume VI for the standard driver interface, if you are not already aware of it.
I was not aware of that indeed. I just had a quick look. If I understand well the ENET driver is not a hardware driver but communicates directly with the hardware drivers.
If I understand well this sums up as :
Mac TCP -> ENET driver -> Nuvotech driver -> SCSI -> 68net
Any feedback on this understanding ?