Interrupts don't 'hit' the uart. Instead uart generates an interrupt (if it is so configured) when it receives a complete character in it's buffer, and the mcu just has to read contents of the RX buffer.
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So config your uart to generate interrupt on full receive, setup the ISR for the isr.
In the isr, read the rx port and store in appropriate ram buffer. Set a flag for main routine to pick up/ read buffer and take action.