pinctrl: single: Add support for wake-up interrupts

The pin control registers can have interrupts for example
for device wake-up. These interrupts can be treated as a
chained interrupt controller as suggested earlier by
Linus Walleij <linus.walleij@linaro.org>.

This patch adds support for interrupts in a way that
should be pretty generic, and works for the omaps that
support wake-up interrupts. On omaps, there's an
interrupt enable and interrupt status bit for each pin.
The two pinctrl domains on omaps share a single interrupt
from the PRM chained interrupt handler. Support for
other similar hardware should be easy to add.

Note that this patch does not attempt to handle the
wake-up interrupts automatically unlike the earlier
patches. This patch allows the device drivers to do
a request_irq() on the wake-up pins as needed. I'll
try to do also a separate generic patch for handling
the wake-up events automatically.

Also note that as this patch makes the pinctrl-single
an irq controller, the current bindings need some
extra trickery to use interrupts from two different
interrupt controllers for the same driver. So it
might be worth waiting a little on the patches
enabling the wake-up interrupts from drivers as there
should be a generic way to handle it coming. And also
there's been discussion of interrupts-extended binding
for using interrupts from multiple interrupt controllers.

In any case, this patch should be ready to go allowing
handling the wake-up interrupts in a generic way, or
separately from the device drivers.

Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Prakash Manjunathappa <prakash.pm@ti.com>
Cc: Roger Quadros <rogerq@ti.com>
Cc: linux-kernel@vger.kernel.org
Cc: Benoît Cousson <bcousson@baylibre.com>
Cc: devicetree@vger.kernel.org
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/pinctrl/pinctrl-single.txt

@@ -72,6 +72,13 @@ Optional properties:
 		/* pin base, nr pins & gpio function */
 		pinctrl-single,gpio-range = <&range 0 3 0 &range 3 9 1>;
 
+- interrupt-controller : standard interrupt controller binding if using
+  interrupts for wake-up events for example. In this case pinctrl-single
+  is set up as a chained interrupt controller and the wake-up interrupts
+  can be requested by the drivers using request_irq().
+
+- #interrupt-cells : standard interrupt binding if using interrupts
+
 This driver assumes that there is only one register for each pin (unless the
 pinctrl-single,bit-per-mux is set), and uses the common pinctrl bindings as
 specified in the pinctrl-bindings.txt document in this directory.
@@ -121,6 +128,8 @@ pmx_core: pinmux@4a100040 {
 	reg = <0x4a100040 0x0196>;
 	#address-cells = <1>;
 	#size-cells = <0>;
+	#interrupt-cells = <1>;
+	interrupt-controller;
 	pinctrl-single,register-width = <16>;
 	pinctrl-single,function-mask = <0xffff>;
 };
@@ -131,6 +140,8 @@ pmx_wkup: pinmux@4a31e040 {
 	reg = <0x4a31e040 0x0038>;
 	#address-cells = <1>;
 	#size-cells = <0>;
+	#interrupt-cells = <1>;
+	interrupt-controller;
 	pinctrl-single,register-width = <16>;
 	pinctrl-single,function-mask = <0xffff>;
 };