mailbox: arm_mhuv3: Add driver

Add support for ARM MHUv3 mailbox controller.

Support is limited to the MHUv3 Doorbell extension using only the PBX/MBX
combined interrupts.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

MAINTAINERS

@@ -12994,6 +12994,15 @@ F:	Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml
 F:	drivers/mailbox/arm_mhuv2.c
 F:	include/linux/mailbox/arm_mhuv2_message.h
 
+MAILBOX ARM MHUv3
+M:	Sudeep Holla <sudeep.holla@arm.com>
+M:	Cristian Marussi <cristian.marussi@arm.com>
+L:	linux-kernel@vger.kernel.org
+L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
+S:	Maintained
+F:	Documentation/devicetree/bindings/mailbox/arm,mhuv3.yaml
+F:	drivers/mailbox/arm_mhuv3.c
+
 MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
 M:	Alejandro Colomar <alx@kernel.org>
 L:	linux-man@vger.kernel.org

drivers/mailbox/Kconfig

@@ -23,6 +23,18 @@ config ARM_MHU_V2
 	  Say Y here if you want to build the ARM MHUv2 controller driver,
 	  which provides unidirectional mailboxes between processing elements.
 
+config ARM_MHU_V3
+	tristate "ARM MHUv3 Mailbox"
+	depends on HAS_IOMEM || COMPILE_TEST
+	depends on OF
+	help
+	  Say Y here if you want to build the ARM MHUv3 controller driver,
+	  which provides unidirectional mailboxes between processing elements.
+
+	  ARM MHUv3 controllers can implement a varying number of extensions
+	  that provides different means of transports: supported extensions
+	  will be discovered and possibly managed at probe-time.
+
 config IMX_MBOX
 	tristate "i.MX Mailbox"
 	depends on ARCH_MXC || COMPILE_TEST

drivers/mailbox/Makefile

@@ -9,6 +9,8 @@ obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o arm_mhu_db.o
 
 obj-$(CONFIG_ARM_MHU_V2)	+= arm_mhuv2.o
 
+obj-$(CONFIG_ARM_MHU_V3)	+= arm_mhuv3.o
+
 obj-$(CONFIG_IMX_MBOX)	+= imx-mailbox.o
 
 obj-$(CONFIG_ARMADA_37XX_RWTM_MBOX)	+= armada-37xx-rwtm-mailbox.o