dt-bindings: renesas: Document preferred compatible naming

Compatibles can come in two formats. Either "vendor,ip-soc" or
"vendor,soc-ip". Add a DT schema file documenting Renesas preferred
policy and enforcing it for all new compatibles, except few existing
patterns.

Suggested-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Niklas Söderlund <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>

Documentation/devicetree/bindings/soc/renesas/renesas-soc.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/renesas/renesas-soc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas SoC compatibles naming convention
+
+maintainers:
+  - Geert Uytterhoeven <[e-mail]>
+  - Niklas Söderlund <[e-mail]>
+
+description: |
+  Guidelines for new compatibles for SoC blocks/components.
+  When adding new compatibles in new bindings, use the format::
+    renesas,SoC-IP
+
+  For example::
+   renesas,r8a77965-csi2
+
+  When adding new compatibles to existing bindings, use the format in the
+  existing binding, even if it contradicts the above.
+
+select:
+  properties:
+    compatible:
+      contains:
+        pattern: "^renesas,.+-.+$"
+  required:
+    - compatible
+
+properties:
+  compatible:
+    minItems: 1
+    maxItems: 4
+    items:
+      anyOf:
+        # Preferred naming style for compatibles of SoC components
+        - pattern: "^renesas,(emev2|r(7s|8a|9a)[a-z0-9]+|rcar|rmobile|rz[a-z0-9]*|sh(7[a-z0-9]+)?|mobile)-[a-z0-9-]+$"
+        - pattern: "^renesas,(condor|falcon|gr-peach|salvator|sk-rz|smar(c(2)?)?|spider|white-hawk)(.*)?$"
+
+        # Legacy compatibles
+        #
+        # New compatibles are not allowed.
+        - pattern: "^renesas,(can|cpg|dmac|du|(g)?ether(avb)?|gpio|hscif|(r)?i[i2]c|imr|intc|ipmmu|irqc|jpu|mmcif|msiof|mtu2|pci(e)?|pfc|pwm|[rq]spi|rcar_sound|sata|scif[ab]*|sdhi|thermal|tmu|tpu|usb(2|hs)?|vin|xhci)-[a-z0-9-]+$"
+        - pattern: "^renesas,(d|s)?bsc(3)?-(r8a73a4|r8a7740|sh73a0)$"
+        - pattern: "^renesas,em-(gio|sti|uart)$"
+        - pattern: "^renesas,fsi2-(r8a7740|sh73a0)$"
+        - pattern: "^renesas,hspi-r8a777[89]$"
+        - pattern: "^renesas,sysc-(r8a73a4|r8a7740|rmobile|sh73a0)$"
+        - enum:
+            - renesas,imr-lx4
+            - renesas,mtu2-r7s72100
+
+        # None SoC component compatibles
+        #
+        # Compatibles with the Renesas vendor prefix that do not relate to any SoC
+        # component are OK. New compatibles are allowed.
+        - enum:
+            - renesas,smp-sram
+
+        # Do not fail compatibles not matching the select pattern
+        #
+        # Some SoC components in addition to a Renesas compatible list
+        # compatibles not related to Renesas. The select pattern for this
+        # schema hits all compatibles that have at lest one Renesas compatible
+        # and try to validate all values in that compatible array, allow all
+        # that don't match the schema select pattern. For example,
+        #
+        #   compatible = "renesas,r9a07g044-mali", "arm,mali-bifrost";
+        - pattern: "^(?!renesas,.+-.+).+$"
+
+additionalProperties: true