drivers: bus: Add Simple Power-Managed Bus DT Bindings

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

diff --git a/Documentation/devicetree/bindings/bus/simple-pm-bus.txt b/Documentation/devicetree/bindings/bus/simple-pm-bus.txt
new file mode 100644 (file)
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+Simple Power-Managed Bus
+========================
+
+A Simple Power-Managed Bus is a transparent bus that doesn't need a real
+driver, as it's typically initialized by the boot loader.
+
+However, its bus controller is part of a PM domain, or under the control of a
+functional clock.  Hence, the bus controller's PM domain and/or clock must be
+enabled for child devices connected to the bus (either on-SoC or externally)
+to function.
+
+While "simple-pm-bus" follows the "simple-bus" set of properties, as specified
+in ePAPR, it is not an extension of "simple-bus".
+
+
+Required properties:
+  - compatible: Must contain at least "simple-pm-bus".
+               Must not contain "simple-bus".
+               It's recommended to let this be preceded by one or more
+               vendor-specific compatible values.
+  - #address-cells, #size-cells, ranges: Must describe the mapping between
+               parent address and child address spaces.
+
+Optional platform-specific properties for clock or PM domain control (at least
+one of them is required):
+  - clocks: Must contain a reference to the functional clock(s),
+  - power-domains: Must contain a reference to the PM domain.
+Please refer to the binding documentation for the clock and/or PM domain
+providers for more details.
+
+
+Example:
+
+       bsc: bus@fec10000 {
+               compatible = "renesas,bsc-sh73a0", "renesas,bsc",
+                            "simple-pm-bus";
+               #address-cells = <1>;
+               #size-cells = <1>;
+               ranges = <0 0 0x20000000>;
+               reg = <0xfec10000 0x400>;
+               interrupts = <0 39 IRQ_TYPE_LEVEL_HIGH>;
+               clocks = <&zb_clk>;
+               power-domains = <&pd_a4s>;
+       };