cmake: shields: introduce shield.yml

While legacy shields are still supported, this introduces a shield.yml
file similar to board.yml that allows to more explicitly declare a
shield and to set some useful metadata such as vendor and full name.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

doc/hardware/porting/shields.rst

@@ -17,13 +17,29 @@ under :zephyr_file:`boards/shields`:
 .. code-block:: none
 
    boards/shields/<shield>
+   ├── shield.yml
    ├── <shield>.overlay
    ├── Kconfig.shield
    ├── Kconfig.defconfig
    └── pre_dt_shield.cmake
 
 These files provides shield configuration as follows:
 
+* **shield.yml**: This file provides metadata about the shield in YAML format.
+  It must contain the following fields:
+
+  * ``name``: Name of the shield used in Kconfig and build system (required)
+  * ``full_name``: Full commercial name of the shield (required)
+  * ``vendor``: Manufacturer/vendor of the shield (required)
+
+  Example:
+
+  .. code-block:: yaml
+
+     name: foo_shield
+     full_name: Foo Shield for Arduino
+     vendor: acme
+
 * **<shield>.overlay**: This file provides a shield description in devicetree
   format that is merged with the board's :ref:`devicetree <dt-guide>`
   before compilation.

scripts/list_shields.py

@@ -6,9 +6,24 @@
 
 import argparse
 import json
+import sys
 from dataclasses import dataclass
 from pathlib import Path
 
+import pykwalify.core
+import yaml
+
+try:
+    from yaml import CSafeLoader as SafeLoader
+except ImportError:
+    from yaml import SafeLoader
+
+SHIELD_SCHEMA_PATH = str(Path(__file__).parent / 'schemas' / 'shield-schema.yml')
+with open(SHIELD_SCHEMA_PATH) as f:
+    shield_schema = yaml.load(f.read(), Loader=SafeLoader)
+
+SHIELD_YML = 'shield.yml'
+
 #
 # This is shared code between the build system's 'shields' target
 # and the 'west shields' extension command. If you change it, make
@@ -22,10 +37,21 @@
 class Shield:
     name: str
     dir: Path
+    full_name: str | None = None
+    vendor: str | None = None
 
 def shield_key(shield):
     return shield.name
 
+def process_shield_data(shield_data, shield_dir):
+    # Create shield from yaml data
+    return Shield(
+        name=shield_data['name'],
+        dir=shield_dir,
+        full_name=shield_data.get('full_name'),
+        vendor=shield_data.get('vendor')
+    )
+
 def find_shields(args):
     ret = []
 
@@ -45,6 +71,28 @@ def find_shields_in(root):
     for maybe_shield in (shields).iterdir():
         if not maybe_shield.is_dir():
             continue
+
+        # Check for shield.yml first
+        shield_yml = maybe_shield / SHIELD_YML
+        if shield_yml.is_file():
+            with shield_yml.open('r', encoding='utf-8') as f:
+                shield_data = yaml.load(f.read(), Loader=SafeLoader)
+
+            try:
+                pykwalify.core.Core(source_data=shield_data, schema_data=shield_schema).validate()
+            except pykwalify.errors.SchemaError as e:
+                sys.exit(f'ERROR: Malformed shield.yml in file: {shield_yml.as_posix()}\n{e}')
+
+            if 'shields' in shield_data:
+                # Multiple shields format
+                for shield_info in shield_data['shields']:
+                    ret.append(process_shield_data(shield_info, maybe_shield))
+            elif 'shield' in shield_data:
+                # Single shield format
+                ret.append(process_shield_data(shield_data['shield'], maybe_shield))
+            continue
+
+        # Fallback to legacy method if no shield.yml
         for maybe_kconfig in maybe_shield.iterdir():
             if maybe_kconfig.name == 'Kconfig.shield':
                 for maybe_overlay in maybe_shield.iterdir():

scripts/schemas/shield-schema.yml

@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: Apache-2.0
+#
+# Copyright The Zephyr Project Contributors
+
+# A pykwalify schema for basic validation of the structure of a shield metadata YAML file.
+#
+# The shield.yml file can contain either a single shield definition or a list of shields.
+
+schema;shield-schema:
+  type: map
+  mapping:
+    name:
+      required: true
+      type: str
+      desc: Name of the shield (used in Kconfig and build system)
+    full_name:
+      required: true
+      type: str
+      desc: Full name of the shield (typically the commercial name)
+    vendor:
+      required: true
+      type: str
+      desc: Manufacturer/vendor of the shield
+
+type: map
+range:
+  min: 1
+  max: 1
+mapping:
+  shield:
+    include: shield-schema
+  shields:
+    type: seq
+    sequence:
+      - include: shield-schema