I ended up figuring out what the problem was - schematic was mislabeled. But for those that are curious how to do it, here's how I did it for pin PB_2:
#define CPU_PORT 11
#define CPU_PORT_PIN 0
#define GPIO_PORT 5
#define GPIO_PIN 22
// Setup CPU port 11, pin 0, with an input buffer, pull down resistor, and function 4 mode.
Chip_SCU_PinMuxSet(CPU_PORT, CPU_PORT_PIN, (SCU_MODE_INBUFF_EN | SCU_MODE_PULLDOWN | SCU_MODE_FUNC4));
// Set GPIO port 5, pin 22, as an input
Chip_GPIO_SetPinDIRInput(LPC_GPIO_PORT, GPIO_PORT, GPIO_PIN);
// Set GPIO port 5, pin 22, as an pin for CPU pin interrupt port 0
Chip_SCU_GPIOIntPinSel(0, GPIO_PORT, GPIO_PIN);
// Clear any pending interrupts on CPU pin interrupt port 0
Chip_PININT_ClearIntStatus(LPC_GPIO_PIN_INT, PININTCH0);
// Set CPU pin interrupt port 0 as edge sensitive
Chip_PININT_SetPinModeEdge(LPC_GPIO_PIN_INT, PININTCH0);
// Set CPU pin interrupt port 0 as high enabled
Chip_PININT_EnableIntHigh(LPC_GPIO_PIN_INT, PININTCH0);
// Clear any pending interrupts in the NVIC for CPU pin interrupts on port 0
NVIC_ClearPendingIRQ(PIN_INT0_IRQn);
// Enable the interrupts in the NVIC for CPU pin interrupts on port 0
NVIC_EnableIRQ(PIN_INT0_IRQn);