drivers: bus: Add Renesas Bus State Controller (BSC) DT Bindings

Renesas Bus State Controller (BSC)

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The Renesas Bus State Controller (BSC, sometimes called "LBSC within Bus

Bridge", or "External Bus Interface") can be found in several Renesas ARM SoCs.

It provides an external bus for connecting multiple external devices to the

SoC, driving several chip select lines, for e.g. NOR FLASH, Ethernet and USB.

While the BSC is a fairly simple memory-mapped bus, it may be part of a PM

domain, and may have a gateable functional clock.

Before a device connected to the BSC can be accessed, the PM domain

containing the BSC must be powered on, and the functional clock

driving the BSC must be enabled.

The bindings for the BSC extend the bindings for "simple-pm-bus".

Required properties

  - compatible: Must contain an SoC-specific value, and "renesas,bsc" and

		"simple-pm-bus" as fallbacks.

                SoC-specific values can be:

		"renesas,bsc-r8a73a4" for R-Mobile APE6 (r8a73a4)

		"renesas,bsc-sh73a0" for SH-Mobile AG5 (sh73a0)

  - #address-cells, #size-cells, ranges: Must describe the mapping between

		parent address and child address spaces.

  - reg: Must contain the base address and length to access the bus controller.

Optional properties:

  - interrupts: Must contain a reference to the BSC interrupt, if available.

  - clocks: Must contain a reference to the functional clock, if available.

  - power-domains: Must contain a reference to the PM domain, if available.

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>;

	};