On Mon, Sep 28, 2009 at 11:58:13AM +0200, Lennert Buytenhek wrote:

Can't you detect whether the 8250 IRQ is routed at boot?  E.g. cause
the UART to throw an interrupt, check the XINT, clear the interrupt,
and check the XINT again, and see if the 8250 interrupt status
corresponds to the XINT or not?  (And then printk the result of the
detection.)

8250 already has support for auto-probing its interrupt.