+ If there is a need to exclude certain GPIOs from the IRQ domain, one can
+ set .irq_need_valid_mask of the gpiochip before gpiochip_add_data() is
+ called. This allocates .irq_valid_mask with as many bits set as there are
+ GPIOs in the chip. Drivers can exclude GPIOs by clearing bits from this
+ mask. The mask must be filled in before gpiochip_irqchip_add() is called.
+