Help needed to port NetBSD to an alien i386 machine

Hello there,

I'd like to port NetBSD-8 to an altos unix machine[0]. Altos has unix
installed and I chose netbsd-8 because I want to be able to run also unix
apps and 8 was the last version that supported ibcs2.

So far I have managed to decompile and patch the BIOS to support 486 DLC as
386 has been supported by NetBSD for a very long time.

I need help with the following:
- how to manually compile the bootloader (sys/arch/i386/stand). I searched
the net but I couldn't find any info...
- even if it's x86 based, this machine is not a PC! It doesn't have ISA,
PIC, IDE, etc. Instead all the communication with all the I/O is done via
DMA and irqs,  therefore I'll need to write drivers for these I/Os. Any
tutorial, examples, documentation will be very much appreciated!
- does the info from https://www.netbsd.org/docs/kernel/ddwg.html still
apply to NetBSD-8 ? If not, where can I find an up to date one?

I don't have experience with NetBSD, though I have quite a lot of
experience with linux, so please give me as many details as possible.

Thanks in advance!

Cheers,
BogDan.


[0]
http://www.bitsavers.org/pdf/altos/386/Altos-386_Series_1000_Brochure_Nov88.pdf