The GIC proxy interrupts are used by the PMU when the RPU and APU cannot service an interrupt because the processor is powered-down.
The GIC proxy interrupts are listed in Table: APU Private Peripheral Interrupts and are controlled by the five sets of interrupt registers in the LPD_GIC_PROXY register set: GICP{0:4}_IRQ_{TRIGGER, STATUS, MASK, ENABLE, DISABLE}. The mask register bits are applied to the status register bits.