Let each of the 8 interrupts set or clock a latch which the '51 can read and reset.
Feed the 8 latch outputs to a nor gate and let the output LEVEL interrupt
the '51 EI0 or EI1. When the '51 detect an interrupt it will read the 8 latches and act upon any set bit and reset the bit acted upon. The '51 will keep interrupting itself till no latches are set. Verify very carefully that you have the time to process the interrupts before going forward with this design.

Have fun,

Erik