i3c: master: Add basic driver for the Renesas I3C controller

Add a basic driver for the I3C controller found in Renesas RZ/G3S and
G3E SoCs. Support I3C pure busses (tested with two targets) and mixed
busses (two I3C devices plus various I2C targets). DAA and communication
with temperature sensors worked reliably at various speeds.

Missing features such as IBI, HotJoin, and target mode will be added
incrementally.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250724094146.6443-5-wsa+renesas@sang-engineering.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

MAINTAINERS

@@ -11458,6 +11458,13 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/i3c/cdns,i3c-master.yaml
 F:	drivers/i3c/master/i3c-master-cdns.c
 
+I3C DRIVER FOR RENESAS
+M:	Wolfram Sang <wsa+renesas@sang-engineering.com>
+M:	Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
+S:	Supported
+F:	Documentation/devicetree/bindings/i3c/renesas,i3c.yaml
+F:	drivers/i3c/master/renesas-i3c.c
+
 I3C DRIVER FOR SYNOPSYS DESIGNWARE
 S:	Orphan
 F:	Documentation/devicetree/bindings/i3c/snps,dw-i3c-master.yaml

drivers/i3c/master/Kconfig

@@ -64,3 +64,13 @@ config MIPI_I3C_HCI_PCI
 
 	  This driver can also be built as a module. If so, the module will be
 	  called mipi-i3c-hci-pci.
+
+config RENESAS_I3C
+	tristate "Renesas I3C controller driver"
+	depends on HAS_IOMEM
+	depends on ARCH_RENESAS || COMPILE_TEST
+	help
+	  Support the Renesas I3C controller as found in some RZ variants.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called renesas-i3c.

drivers/i3c/master/Makefile

@@ -4,3 +4,4 @@ obj-$(CONFIG_DW_I3C_MASTER)		+= dw-i3c-master.o
 obj-$(CONFIG_AST2600_I3C_MASTER)	+= ast2600-i3c-master.o
 obj-$(CONFIG_SVC_I3C_MASTER)		+= svc-i3c-master.o
 obj-$(CONFIG_MIPI_I3C_HCI)		+= mipi-i3c-hci/
+obj-$(CONFIG_RENESAS_I3C)		+= renesas-i3c.o