root@rp3440:~# lspci -nn
[...]
e0:01.0 Communication controller [0780]: Hewlett-Packard Company Auxiliary Diva Serial Port [103c:1290] (rev 01)
e0:01.1 Serial controller [0700]: Hewlett-Packard Company Diva Serial [GSP] Multiport UART [103c:1048] (rev 03)
Interesting - actually the current situation looks like what [your patch from May 29th] should have accomplished. But as you dropped it in favor of a patch to palo, it seems to be unrelated.
[your patch from May 29th]:https://patchwork.kernel.org/patch/9753613/
The patch had some other issues which is why I dropped it.
I like the testing of the class id much more, as it's done by the current upstream code.
E.g. this diva port reports PCI_CLASS_COMMUNICATION_OTHER as PCI CLASS ID, which differs to what the serial port driver should handle.