[coreboot - Feature #331] (New) Add detail wiki how to use oxford serial card?

Issue #331 has been reported by xinhua wang.

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Feature #331: Add detail wiki how to use oxford serial card? 
https://ticket.coreboot.org/issues/331

* Author: xinhua wang
* Status: New
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
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Add detail wiki how to use oxford serial card?

For example, early pci settings.. how to determine what mmio to use, etc

for the green one, I only see

[    0.364949] 0000:01:00.0: ttyS4 at MMIO 0x83401000 (irq = 16, base_baud = 4000000) is a 16C950/954
[    0.365132] 0000:01:00.0: ttyS5 at MMIO 0x83401200 (irq = 16, base_baud = 4000000) is a 16C950/954

then I am lost at what to do, I tried plug in 0x83401000, and select 0 index but it does not do anything

I tested the ttyS4 with another computer and my cable, adapter works.