soc: ti: Add ti_sci_pm_domains driver

Introduce a ti_sci_pm_domains driver to act as a generic pm domain
provider to allow each device to attach and associate it's ti-sci-id so
that it can be controlled through the TI SCI protocol.

This driver implements a simple genpd where each device node has a
phandle to the power domain node and also must provide an index which
represents the ID to be passed with TI SCI representing the device using
a single phandle cell. The driver manually parses the phandle to get the
cell value. Through this interface the genpd dev_ops start and stop
hooks will use TI SCI to turn on and off each device as determined by
pm_runtime usage.

Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
diff --git a/drivers/soc/ti/Kconfig b/drivers/soc/ti/Kconfig
index 3557c5e..39e152a 100644
--- a/drivers/soc/ti/Kconfig
+++ b/drivers/soc/ti/Kconfig
@@ -38,4 +38,16 @@
 	  to communicate and use the Wakeup M3 for PM features like suspend
 	  resume and boots it using wkup_m3_rproc driver.
 
+config TI_SCI_PM_DOMAINS
+	tristate "TI SCI PM Domains Driver"
+	depends on TI_SCI_PROTOCOL
+	depends on PM_GENERIC_DOMAINS
+	help
+	  Generic power domain implementation for TI device implementing
+	  the TI SCI protocol.
+
+	  To compile this as a module, choose M here. The module will be
+	  called ti_sci_pm_domains. Note this is needed early in boot before
+	  rootfs may be available.
+
 endif # SOC_TI