ARM: mvebu: add Device Tree description of RTC on Armada 38x

The Marvell Armada 38x SoCs contains an RTC which differs from the RTC
used in the other mvebu SoCs until now.  This commit adds the Device Tree
description of this interface at the SoC level.
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: Arnaud Ebalard <arno@natisbad.org>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Boris BREZILLON <boris.brezillon@free-electrons.com>
Cc: Lior Amsalem <alior@marvell.com>
Cc: Tawfik Bayouk <tawfik@marvell.com>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/boot/dts/armada-38x.dtsi

@@ -381,6 +381,13 @@ mdio {
 				clocks = <&gateclk 4>;
 			};
 
+			rtc@a3800 {
+				compatible = "marvell,armada-380-rtc";
+				reg = <0xa3800 0x20>, <0x184a0 0x0c>;
+				reg-names = "rtc", "rtc-soc";
+				interrupts = <GIC_SPI 21 IRQ_TYPE_LEVEL_HIGH>;
+			};
+
 			sata@a8000 {
 				compatible = "marvell,armada-380-ahci";
 				reg = <0xa8000 0x2000>;