dt-bindings: aspeed-lpc: Add reset controller

This describes the reset controller present in the LPC address space.
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NJoel Stanley <joel@jms.id.au>
[p.zabel@pengutronix.de: removed a space before tab in indent]
Signed-off-by: NPhilipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/mfd/aspeed-lpc.txt

@@ -135,3 +135,24 @@ lhc: lhc@20 {
 	compatible = "aspeed,ast2500-lhc";
 	reg = <0x20 0x24 0x48 0x8>;
 };
+
+LPC reset control
+-----------------
+
+The UARTs present in the ASPEED SoC can have their resets tied to the reset
+state of the LPC bus. Some systems may chose to modify this configuration.
+
+Required properties:
+
+ - compatible:		"aspeed,ast2500-lpc-reset" or
+			"aspeed,ast2400-lpc-reset"
+ - reg:			offset and length of the IP in the LHC memory region
+ - #reset-controller	indicates the number of reset cells expected
+
+Example:
+
+lpc_reset: reset-controller@18 {
+        compatible = "aspeed,ast2500-lpc-reset";
+        reg = <0x18 0x4>;
+        #reset-cells = <1>;
+};