mailbox: arm_mhuv2: Add driver

This adds driver for the ARM MHUv2 (Message Handling Unit) mailbox
controller.

This is based on the accepted DT bindings of the controller and supports
combination of both transport protocols, i.e. doorbell and data-transfer.

Transmitting and receiving data through the mailbox framework is done
through struct arm_mhuv2_mbox_msg.

Based on the initial work done by Morten Borup Petersen from ARM.

Co-developed-by: Tushar Khandelwal <[email protected]>
Signed-off-by: Tushar Khandelwal <[email protected]>
Tested-by: Usama Arif <[email protected]>
Signed-off-by: Viresh Kumar <[email protected]>
Signed-off-by: Jassi Brar <[email protected]>

MAINTAINERS

@@ -10418,6 +10418,15 @@ F:	drivers/mailbox/
 F:	include/linux/mailbox_client.h
 F:	include/linux/mailbox_controller.h
 
+MAILBOX ARM MHUv2
+M:	Viresh Kumar <[email protected]>
+M:	Tushar Khandelwal <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	drivers/mailbox/arm_mhuv2.c
+F:	include/linux/mailbox/arm_mhuv2_message.h
+F:	Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml
+
 MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
 M:	Michael Kerrisk <[email protected]>
 L:	[email protected]

drivers/mailbox/Kconfig

@@ -16,6 +16,13 @@ config ARM_MHU
 	  The controller has 3 mailbox channels, the last of which can be
 	  used in Secure mode only.
 
+config ARM_MHU_V2
+	tristate "ARM MHUv2 Mailbox"
+	depends on ARM_AMBA
+	help
+	  Say Y here if you want to build the ARM MHUv2 controller driver,
+	  which provides unidirectional mailboxes between processing elements.
+
 config IMX_MBOX
 	tristate "i.MX Mailbox"
 	depends on ARCH_MXC || COMPILE_TEST

drivers/mailbox/Makefile

@@ -7,6 +7,8 @@ obj-$(CONFIG_MAILBOX_TEST)	+= mailbox-test.o
 
 obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o arm_mhu_db.o
 
+obj-$(CONFIG_ARM_MHU_V2)	+= arm_mhuv2.o
+
 obj-$(CONFIG_IMX_MBOX)	+= imx-mailbox.o
 
 obj-$(CONFIG_ARMADA_37XX_RWTM_MBOX)	+= armada-37xx-rwtm-mailbox.o