The Crystal Cove PMIC has a pin which can be used to connect the IRQ of
an external charger IC. On some boards this is used so we need a way to
look this up.

Note that the Intel PMICs have 2 levels of interrupts and thus
2 levels of IRQ domains all tied to a single fwnode.

Level 1 is the irqchip which demultiplexes the actual PMIC interrupt into
interrupts for the various MFD cells. Level 2 are the irqchips used in the
cell drivers which themselves export IRQs, such as the crystal_cove_gpio
driver, which de-multiplexes the level 2 interrupts for the GPIOs into
individual per GPIO IRQs.

The crystal_cove_charger driver registers an irqchip with a single IRQ for
the charger driver to consume. Note the MFD cell IRQ cannot be consumed
directly because the level 2 interrupts must be explicitly acked.

To allow finding the right IRQ domain when looking up the IRQ for
the charger, the crystal_cove_charger driver sets a DOMAIN_BUS_WIRED token
on its IRQ domain.

Add support for looking up the IRQ from the crystal_cove_charger driver.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20211229231431.437982-6-hdegoede@redhat.com