I simply want a standard PC interface that is straightforward to work with and gives me higher data rates than 16550-based RS232
About 3 years ago while working with files at a long forgotten place, I posted the brand of a PC serial interface that ran 4 times faster than the standard. I have NO recollection what it was, but it was used to drive Lauterbach ARM ICE.

In other words it exist, maybe lauterbach has a link since their ICE can handle the speed

Erik