SSIA. I had a quick look and I cound't see anything for it. Serial port access is notoriously OS-specific. On UNIX there is termio and on Windows you have overlapped versus non-overlap IO for either Windows normal or Windows embedded. So this is just the sort of thing I hoped Poco would have support for.
I looked at previous posts that mentioned 'serial' but didn't find very much. Looks like it was discussed briefly last year but no obvious conclusion.