It depends from the nature of the interrupt sources:

If they are really fast (<10µsec), then OR-ing may be a solution. But I fear, the 8051 was unable to handle 16 very fast interrupt sources simultaneous.


But if they are snail slow (>100µsec) like keys or contacts or so, then the usual way was to combine scanning and debouncing into a single timer interrupt.
Search for "debouncing" if you want this.



Peter