How to set interrupt for a particular GPIO pin?

What could be the equivalent code for the below code snippet

// Set up RX interrupts, but only if we have a valid RX baud rate
if (_rx_delay_stopbit)
if (digitalPinToPCICR(_receivePin))
*digitalPinToPCICR(_receivePin) |= _BV(digitalPinToPCICRbit(_receivePin));
*digitalPinToPCMSK(_receivePin) |= _BV(digitalPinToPCMSKbit(_receivePin));
tunedDelay(_tx_delay); // if we were low this establishes the end

What should i do for interrupt? where can i get some ideas about interrupt enabling?

And also i have this

#define digitalPinToInterrupt§ (INT_GPIO_BASE + variant_pin_map[P].bit_pos)

taken from the arduino variants.