scripts: dts: Refactor gen_driver_kconfig_dts

The motivation for this patch was to improve the script's performance,
but some stylistic changes and cleanups are included as well.

The main optimization concerns the use of PyYAML, as it offers multiple
functions for interpreting YAML. The commonly used `load`/`safe_load`
converts a YAML stream to a dictionary. There are also `scan`, `parse`,
and `compose`, which return intermediate representations, the last one
being a graph. [1]

Since `gen_driver_kconfig_dts` scans DT bindings for compatible strings,
it only needs to look through top level keys in YAML. The intermediate
PyYAML graph is sufficient for this, and using it reduces the script's
execution time by about 30%, without making the code too complicated.

[1] - https://pyyaml.org/wiki/PyYAMLDocumentation

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>

scripts/dts/gen_driver_kconfig_dts.py

@@ -1,13 +1,12 @@
 #!/usr/bin/env python3
 #
 # Copyright (c) 2022 Kumar Gala <galak@kernel.org>
+# Copyright (c) 2025 Nordic Semiconductor ASA
 #
 # SPDX-License-Identifier: Apache-2.0
 
 import argparse
 import os
-import sys
-import re
 
 import yaml
 try:
@@ -16,22 +15,33 @@ try:
 except ImportError:
     from yaml import SafeLoader     # type: ignore
 
-sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'python-devicetree',
-                                'src'))
+
+HEADER = """\
+# Generated devicetree Kconfig
+#
+# SPDX-License-Identifier: Apache-2.0"""
+
+
+KCONFIG_TEMPLATE = """
+DT_COMPAT_{COMPAT} := {compat}
+
+config DT_HAS_{COMPAT}_ENABLED
+\tdef_bool $(dt_compat_enabled,$(DT_COMPAT_{COMPAT}))"""
+
+
+# Character translation table used to derive Kconfig symbol names
+TO_UNDERSCORES = str.maketrans("-,.@/+", "______")
+
 
 def binding_paths(bindings_dirs):
-    # Returns a list with the paths to all bindings (.yaml files) in
-    # 'bindings_dirs'
-
-    binding_paths = []
+    # Yields paths to all bindings (.yaml files) in 'bindings_dirs'
 
     for bindings_dir in bindings_dirs:
         for root, _, filenames in os.walk(bindings_dir):
             for filename in filenames:
-                if filename.endswith(".yaml") or filename.endswith(".yml"):
-                    binding_paths.append(os.path.join(root, filename))
+                if filename.endswith((".yaml", ".yml")):
+                    yield os.path.join(root, filename)
 
-    return binding_paths
 
 def parse_args():
     # Returns parsed command-line arguments
@@ -45,56 +55,38 @@ def parse_args():
 
     return parser.parse_args()
 
-def printfile(s):
-    print(s, file=kconfig_file)
-
-def str2ident(s):
-    # Converts 's' to a form suitable for (part of) an identifier
-
-    return re.sub('[-,.@/+]', '_', s.upper())
-
-def compat2kconfig(compat):
-    compat_ident = str2ident(compat)
-
-    printfile(f'')
-    printfile(f'DT_COMPAT_{compat_ident} := {compat}')
-    printfile(f'')
-    printfile(f'config DT_HAS_{compat_ident}_ENABLED')
-    printfile(f'\tdef_bool $(dt_compat_enabled,$(DT_COMPAT_{compat_ident}))')
 
 def main():
-    global kconfig_file
     args = parse_args()
 
-    compat_list = []
+    compats = set()
 
     for binding_path in binding_paths(args.bindings_dirs):
         with open(binding_path, encoding="utf-8") as f:
-            contents = f.read()
-
             try:
-                # Parsed PyYAML output (Python lists/dictionaries/strings/etc.,
-                # representing the file)
-                raw = yaml.load(contents, Loader=SafeLoader)
+                # Parsed PyYAML representation graph. For our purpose,
+                # we don't need the whole file converted into a dict.
+                root = yaml.compose(f, Loader=SafeLoader)
             except yaml.YAMLError as e:
                 print(f"WARNING: '{binding_path}' appears in binding "
                       f"directories but isn't valid YAML: {e}")
                 continue
-        if raw is None or 'compatible' not in raw:
+
+        if not isinstance(root, yaml.MappingNode):
             continue
-
-        compat_list.append(raw['compatible'])
-
-    # Remove any duplicates and sort the list
-    compat_list = sorted(set(compat_list))
+        for key, node in root.value:
+            if key.value == "compatible" and isinstance(node, yaml.ScalarNode):
+                compats.add(node.value)
+                break
 
     with open(args.kconfig_out, "w", encoding="utf-8") as kconfig_file:
-        printfile(f'# Generated devicetree Kconfig')
-        printfile(f'#')
-        printfile(f'# SPDX-License-Identifier: Apache-2.0')
+        print(HEADER, file=kconfig_file)
 
-        for c in compat_list:
-            compat2kconfig(c)
+        for c in sorted(compats):
+            out = KCONFIG_TEMPLATE.format(
+                compat=c, COMPAT=c.upper().translate(TO_UNDERSCORES)
+            )
+            print(out, file=kconfig_file)
 
 
 if __name__ == "__main__":