dt-bindings: gpu: add bindings for the ARM Mali Bifrost GPU

Add the bindings for the Bifrost family of ARM Mali GPUs.

The Bifrost GPU architecture is similar to the Midgard family,
but with a different Shader Core & Execution Engine structures.

Bindings are based on the Midgard family bindings, but the inner
architectural changes makes it a separate family needing separate
bindings.

The Bifrost GPUs are present in a number of recent SoCs, like the
Amlogic G12A Family, and many other vendors.
The Amlogic vendor specific compatible is added to handle the
specific IP integration differences and dependencies.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
[narmstrong: fixed small typo in compatible description]
Link: https://patchwork.freedesktop.org/patch/msgid/20190401080949.14550-1-narmstrong@baylibre.com

Documentation/devicetree/bindings/gpu/arm,mali-bifrost.txt

+ARM Mali Bifrost GPU
+====================
+
+Required properties:
+
+- compatible :
+  * Since Mali Bifrost GPU model/revision is fully discoverable by reading
+    some determined registers, must contain the following:
+    + "arm,mali-bifrost"
+  * which must be preceded by one of the following vendor specifics:
+    + "amlogic,meson-g12a-mali"
+
+- reg : Physical base address of the device and length of the register area.
+
+- interrupts : Contains the three IRQ lines required by Mali Bifrost devices,
+  in the following defined order.
+
+- interrupt-names : Contains the names of IRQ resources in this exact defined
+  order: "job", "mmu", "gpu".
+
+Optional properties:
+
+- clocks : Phandle to clock for the Mali Bifrost device.
+
+- mali-supply : Phandle to regulator for the Mali device. Refer to
+  Documentation/devicetree/bindings/regulator/regulator.txt for details.
+
+- operating-points-v2 : Refer to Documentation/devicetree/bindings/opp/opp.txt
+  for details.
+
+- resets : Phandle of the GPU reset line.
+
+Vendor-specific bindings
+------------------------
+
+The Mali GPU is integrated very differently from one SoC to
+another. In order to accommodate those differences, you have the option
+to specify one more vendor-specific compatible, among:
+
+- "amlogic,meson-g12a-mali"
+  Required properties:
+  - resets : Should contain phandles of :
+    + GPU reset line
+    + GPU APB glue reset line
+
+Example for a Mali-G31:
+
+gpu@ffa30000 {
+	compatible = "amlogic,meson-g12a-mali", "arm,mali-bifrost";
+	reg = <0xffe40000 0x10000>;
+	interrupts = <GIC_SPI 160 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 161 IRQ_TYPE_LEVEL_HIGH>,
+		     <GIC_SPI 162 IRQ_TYPE_LEVEL_HIGH>;
+	interrupt-names = "job", "mmu", "gpu";
+	clocks = <&clk CLKID_MALI>;
+	mali-supply = <&vdd_gpu>;
+	operating-points-v2 = <&gpu_opp_table>;
+	resets = <&reset RESET_DVALIN_CAPB3>, <&reset RESET_DVALIN>;
+};
+
+gpu_opp_table: opp_table0 {
+	compatible = "operating-points-v2";
+
+	opp@533000000 {
+		opp-hz = /bits/ 64 <533000000>;
+		opp-microvolt = <1250000>;
+	};
+	opp@450000000 {
+		opp-hz = /bits/ 64 <450000000>;
+		opp-microvolt = <1150000>;
+	};
+	opp@400000000 {
+		opp-hz = /bits/ 64 <400000000>;
+		opp-microvolt = <1125000>;
+	};
+	opp@350000000 {
+		opp-hz = /bits/ 64 <350000000>;
+		opp-microvolt = <1075000>;
+	};
+	opp@266000000 {
+		opp-hz = /bits/ 64 <266000000>;
+		opp-microvolt = <1025000>;
+	};
+	opp@160000000 {
+		opp-hz = /bits/ 64 <160000000>;
+		opp-microvolt = <925000>;
+	};
+	opp@100000000 {
+		opp-hz = /bits/ 64 <100000000>;
+		opp-microvolt = <912500>;
+	};
+};