Use of MmMapIoSpace,HalTranslateBusAddress?

FUNCTIONS:
MmMapIoSpace, HalTranslateBusAddress, WRITE_PORT_ULONG are connected
together through some of their arguments.

I need this function for DMA access to the serial port!! (I hope it’s
possible this way).
How can I determine the port address (let’s say COM2) ???
Can someone fill in this functions specifically for serial port I didn’t
find any resource that would show this thing?!
I’m really stucked here and can’t move on.

Can someone help me please!!!

How can I get the address of serial port and write/read to/from this address
on the most easiest way?

Regards,
Neno