property, and a #gpio-cells integer property, which indicates the number of
cells in a gpio-specifier.
+Some system-on-chips (SoCs) use the concept of GPIO banks. A GPIO bank is an
+instance of a hardware IP core on a silicon die, usually exposed to the
+programmer as a coherent range of I/O addresses. Usually each such bank is
+exposed in the device tree as an individual gpio-controller node, reflecting
+the fact that the hardware was synthesized by reusing the same IP block a
+few times over.
+
+A GPIO controller may specify a bank ID. This is a hardware index that
+indicate the logical order of the GPIO controller in the hardware architecture,
+usually in the sequence 0, 1, 2 .. n. The hardware index may be different
+from the order of register ranges and related to the backplane of how this
+one bank is connected to the outside through a pin controller for example.
+
Optionally, a GPIO controller may have a "ngpios" property. This property
indicates the number of in-use slots of available slots for GPIOs. The
typical example is something like this: the hardware register is 32 bits
reg = <0x00000000 0x1000>;
gpio-controller;
#gpio-cells = <2>;
+ gpio-bank = <0>;
ngpios = <18>;
}