clk: vc5: Add bindings for IDT VersaClock 5P49V5923 and 5P49V5933

Add bindings for IDT VersaClock 5 5P49V5923 and 5P49V5933 chips.
These are I2C clock generators with optional clock source from
either XTal or dedicated clock generator and, depending on the
model, two or more clock outputs.
Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: devicetree@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

Documentation/devicetree/bindings/clock/idt,versaclock5.txt

+Binding for IDT VersaClock5 programmable i2c clock generator.
+
+The IDT VersaClock5 are programmable i2c clock generators providing
+from 3 to 12 output clocks.
+
+==I2C device node==
+
+Required properties:
+- compatible:	shall be one of "idt,5p49v5923" , "idt,5p49v5933".
+- reg:		i2c device address, shall be 0x68 or 0x6a.
+- #clock-cells:	from common clock binding; shall be set to 1.
+- clocks:	from common clock binding; list of parent clock handles,
+		- 5p49v5923: (required) either or both of XTAL or CLKIN
+					reference clock.
+		- 5p49v5933: (optional) property not present (internal
+					Xtal used) or CLKIN reference
+					clock.
+- clock-names:	from common clock binding; clock input names, can be
+		- 5p49v5923: (required) either or both of "xin", "clkin".
+		- 5p49v5933: (optional) property not present or "clkin".
+
+==Mapping between clock specifier and physical pins==
+
+When referencing the provided clock in the DT using phandle and
+clock specifier, the following mapping applies:
+
+5P49V5923:
+	0 -- OUT0_SEL_I2CB
+	1 -- OUT1
+	2 -- OUT2
+
+5P49V5933:
+	0 -- OUT0_SEL_I2CB
+	1 -- OUT1
+	2 -- OUT4
+
+==Example==
+
+/* 25MHz reference crystal */
+ref25: ref25m {
+	compatible = "fixed-clock";
+	#clock-cells = <0>;
+	clock-frequency = <25000000>;
+};
+
+i2c-master-node {
+
+	/* IDT 5P49V5923 i2c clock generator */
+	vc5: clock-generator@6a {
+		compatible = "idt,5p49v5923";
+		reg = <0x6a>;
+		#clock-cells = <1>;
+
+		/* Connect XIN input to 25MHz reference */
+		clocks = <&ref25m>;
+		clock-names = "xin";
+	};
+};
+
+/* Consumer referencing the 5P49V5923 pin OUT1 */
+consumer {
+	...
+	clocks = <&vc5 1>;
+	...
+}