Add Message-Handling-Unit driver for platform variants as mailbox controller.
Actually, only the Amlogic Meson GXBB SoC MHU is supported.

Signed-off-by: Neil Armstrong <redacted>
---
 drivers/mailbox/Kconfig        |  10 ++
 drivers/mailbox/Makefile       |   2 +
 drivers/mailbox/platform_mhu.c | 203 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 215 insertions(+)
 create mode 100644 drivers/mailbox/platform_mhu.c

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 97c3729..4cc93c6 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig

@@ -15,6 +15,16 @@ config ARM_MHU
 	  The controller has 3 mailbox channels, the last of which can be
 	  used in Secure mode only.
 
+config PLATFORM_MHU
+	tristate "Platform MHU Mailbox"
+	depends on OF
+	depends on HAS_IOMEM
+	help
+	  Say Y here if you want to build a platform specific variant MHU
+	  controller driver.
+	  The controller has a maximum of 3 mailbox channels, the last of
+	  which can be used in Secure mode only.
+
 config PL320_MBOX
 	bool "ARM PL320 Mailbox"
 	depends on ARM_AMBA

diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 66c38e3..ace6fed 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile

@@ -6,6 +6,8 @@ obj-$(CONFIG_MAILBOX_TEST)	+= mailbox-test.o
 
 obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o
 
+obj-$(CONFIG_PLATFORM_MHU)	+= platform_mhu.o
+
 obj-$(CONFIG_PL320_MBOX)	+= pl320-ipc.o
 
 obj-$(CONFIG_OMAP2PLUS_MBOX)	+= omap-mailbox.o

diff --git a/drivers/mailbox/platform_mhu.c b/drivers/mailbox/platform_mhu.c
new file mode 100644
index 0000000..d657a50
--- /dev/null
+++ b/drivers/mailbox/platform_mhu.c

@@ -0,0 +1,203 @@
+/*
+ * Copyright (C) 2016 BayLibre SAS.
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ * Heavily based on arm_mhu.c from :
+ * Copyright (C) 2013-2015 Fujitsu Semiconductor Ltd.
+ * Copyright (C) 2015 Linaro Ltd.
+ * Author: Jassi Brar <jaswinder.singh@linaro.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/mailbox_controller.h>
+
+#define INTR_SET_OFS	0x0
+#define INTR_STAT_OFS	0x4
+#define INTR_CLR_OFS	0x8
+
+#define MHU_LP_OFFSET	0x10
+#define MHU_HP_OFFSET	0x1c
+
+#define TX_REG_OFFSET	0x24
+
+#define MHU_CHANS	2
+
+struct platform_mhu_link {
+	unsigned int irq;