Jos van de Ven posted such a patch on the linux-smp mailinglist about a year ago. Fortunately the patch still applies and solves my problem completely. This makes interrupt sharing hard, as two devices could do this simultaneously resulting in only one interrupt, leaving you to wonder if one or several devices need attention. ISA devices works like this. Two simultaneous interrupts may seem unlikely, but keep in mind that this problem also occur if the second interrupt happens while the first is being serviced.
Some interrupt handlers takes a long time, and some devices makes lots of interrupts.
Having one of either kind sharing is a recipe for disaster. This makes interrupt sharing easier. Two or more devices sharing an interrupt can both pull the voltage up. One of them will have its device driver called. The driver will do whatever the device needs, and turn off its interrupt signal.