There is a midway approach between external interrupts and the standard polling. You can generate a periodical interrupt using a timer, say every 10 ms. The ISR polls every keyboard button and if some of them is active, then it ...

option 1) ... generates an external interrupt by SW.

option 2) ... sets a flag bit, so that the main program only has to test one flag bit for all the inputs.

Alfredo del Rio.