bus: ti-sysc: Add minimal TI sysc interconnect target driver

We can handle the sysc interconnect target module in a generic way
for many TI SoCs. Initially let's just enable runtime PM with
autosuspend, and probe the children. This can already be used for
idling interconnect target modules that don't have any device driver
available for the child devices.

For now, the "ti,hwmods" custom binding is still required. That will
be eventually deprecated in later patches. And more features will be
added, such as parsing for sysc capabilities so we can continue
removing the legacy platform data.

Cc: Benoît Cousson <bcousson@baylibre.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Matthijs van Duin <matthijsvanduin@gmail.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: Tero Kristo <t-kristo@ti.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/Kconfig

@@ -104,6 +104,7 @@ config ARCH_OMAP2PLUS
 	select OMAP_GPMC
 	select PINCTRL
 	select SOC_BUS
+	select TI_SYSC
 	select OMAP_IRQCHIP
 	select CLKSRC_TI_32K
 	help

drivers/bus/Kconfig

@@ -157,6 +157,13 @@ config TEGRA_GMI
 	  Driver for the Tegra Generic Memory Interface bus which can be used
 	  to attach devices such as NOR, UART, FPGA and more.
 
+config TI_SYSC
+	bool "TI sysc interconnect target module driver"
+	depends on ARCH_OMAP2PLUS
+	help
+	  Generic driver for Texas Instruments interconnect target module
+	  found on many TI SoCs.
+
 config UNIPHIER_SYSTEM_BUS
 	tristate "UniPhier System Bus driver"
 	depends on ARCH_UNIPHIER && OF

drivers/bus/Makefile

@@ -20,6 +20,7 @@ obj-$(CONFIG_SUNXI_RSB)		+= sunxi-rsb.o
 obj-$(CONFIG_SIMPLE_PM_BUS)	+= simple-pm-bus.o
 obj-$(CONFIG_TEGRA_ACONNECT)	+= tegra-aconnect.o
 obj-$(CONFIG_TEGRA_GMI)		+= tegra-gmi.o
+obj-$(CONFIG_TI_SYSC)		+= ti-sysc.o
 obj-$(CONFIG_UNIPHIER_SYSTEM_BUS)	+= uniphier-system-bus.o
 obj-$(CONFIG_VEXPRESS_CONFIG)	+= vexpress-config.o