dt-bindings: interconnect: Add bindings for imx8m noc

Add initial dt bindings for the interconnects inside i.MX chips.
Multiple external IPs are involved but SOC integration means the
software controllable interfaces are very similar.

Main NOC node acts as interconnect provider if #interconnect-cells is
present. Currently there is a single imx interconnect provider for the
whole SOC.

Other pieces of scalable interconnects can be present, each with their
own OPP table.

Signed-off-by: Leonard Crestez <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/8b341d9[e-mail]
Signed-off-by: Georgi Djakov <[e-mail]>

Documentation/devicetree/bindings/interconnect/fsl,imx8m-noc.yaml

···
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interconnect/fsl,imx8m-noc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic i.MX bus frequency device
+
+maintainers:
+  - Leonard Crestez <[e-mail]>
+
+description: |
+  The i.MX SoC family has multiple buses for which clock frequency (and
+  sometimes voltage) can be adjusted.
+
+  Some of those buses expose register areas mentioned in the memory maps as GPV
+  ("Global Programmers View") but not all. Access to this area might be denied
+  for normal (non-secure) world.
+
+  The buses are based on externally licensed IPs such as ARM NIC-301 and
+  Arteris FlexNOC but DT bindings are specific to the integration of these bus
+  interconnect IPs into imx SOCs.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+        - enum:
+          - fsl,imx8mn-nic
+          - fsl,imx8mm-nic
+          - fsl,imx8mq-nic
+        - const: fsl,imx8m-nic
+      - items:
+        - enum:
+          - fsl,imx8mn-noc
+          - fsl,imx8mm-noc
+          - fsl,imx8mq-noc
+        - const: fsl,imx8m-noc
+      - const: fsl,imx8m-nic
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  operating-points-v2: true
+  opp-table: true
+
+  fsl,ddrc:
+    $ref: "/schemas/types.yaml#/definitions/phandle"
+    description:
+      Phandle to DDR Controller.
+
+  '#interconnect-cells':
+    description:
+      If specified then also act as an interconnect provider. Should only be
+      set once per soc on the main noc.
+    const: 1
+
+required:
+  - compatible
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/imx8mm-clock.h>
+    #include <dt-bindings/interconnect/imx8mm.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    noc: interconnect@32700000 {
+        compatible = "fsl,imx8mm-noc", "fsl,imx8m-noc";
+        reg = <0x32700000 0x100000>;
+        clocks = <&clk IMX8MM_CLK_NOC>;
+        #interconnect-cells = <1>;
+        fsl,ddrc = <&ddrc>;
+
+        operating-points-v2 = <&noc_opp_table>;
+        noc_opp_table: opp-table {
+            compatible = "operating-points-v2";
+
+            opp-133M {
+                opp-hz = /bits/ 64 <133333333>;
+            };
+            opp-800M {
+                opp-hz = /bits/ 64 <800000000>;
+            };
+        };
+    };
+
+    ddrc: memory-controller@3d400000 {
+        compatible = "fsl,imx8mm-ddrc", "fsl,imx8m-ddrc";
+        reg = <0x3d400000 0x400000>;
+        clock-names = "core", "pll", "alt", "apb";
+        clocks = <&clk IMX8MM_CLK_DRAM_CORE>,
+                 <&clk IMX8MM_DRAM_PLL>,
+                 <&clk IMX8MM_CLK_DRAM_ALT>,
+                 <&clk IMX8MM_CLK_DRAM_APB>;
+    };