scripts: Add advanced docs checker to validate all links

- Check if all links are usable and point to existing items
- Check if references work

Signed-off-by: Arkadiusz Balys <arkadiusz.balys@nordicsemi.no>

Author: ArekBalysNordic

docs/checks/conf.py

@@ -0,0 +1,73 @@
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+# Sphinx configuration overlay used by the documentation links check
+# (scripts/matter_sample_checker/checks/docs/check_doc_links.py).
+# This file must be named conf.py because Sphinx requires that name in -c DIR.
+# Imports the production conf.py, then enables strict cross-reference checking
+# and optional intersphinx mappings to locally built NCS docset inventories.
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+DOCS_DIR = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(DOCS_DIR))
+sys.path.insert(0, str(DOCS_DIR / "_extensions"))
+
+from conf import *  # noqa: F401,F403
+
+extensions = list(extensions)
+if "sphinx.ext.intersphinx" not in extensions:
+    extensions.append("sphinx.ext.intersphinx")
+
+# Paths in conf.py are relative to docs/, but Sphinx resolves some settings against
+# the -c directory (docs/checks/). Re-root those entries for link-check builds.
+html_extra_path = [str(DOCS_DIR / "versions.json")]
+templates_path = [str(DOCS_DIR / "_templates")]
+breathe_projects = {"ncs-matter": str(DOCS_DIR / "_build_doxygen" / "xml")}
+
+# Do not suppress missing :ref:, :doc:, or :option: warnings during link checks.
+suppress_warnings = []
+
+NCS_ROOT = DOCS_DIR.parent.parent
+intersphinx_mapping: dict[str, tuple[str, str]] = {}
+
+_DOCSET_INVENTORIES = (
+    ("nrf", "nrf/doc/_build/html/nrf/objects.inv"),
+    ("zephyr", "nrf/doc/_build/html/zephyr/objects.inv"),
+    ("kconfig", "nrf/doc/_build/html/kconfig/objects.inv"),
+    ("nrfxlib", "nrf/doc/_build/html/nrfxlib/objects.inv"),
+    ("mcuboot", "nrf/doc/_build/html/mcuboot/objects.inv"),
+    ("tfm", "nrf/doc/_build/html/tfm/objects.inv"),
+    ("matter", "nrf/doc/_build/html/matter/objects.inv"),
+)
+
+for docset, rel_path in _DOCSET_INVENTORIES:
+    inventory = NCS_ROOT / rel_path
+    if inventory.is_file():
+        intersphinx_mapping[docset] = (f"../{docset}", str(inventory))
+
+# Align with sdk-nrf linkcheck defaults where practical.
+linkcheck_ignore = [
+    # Relative links resolved by intersphinx or Doxygen.
+    r"\.\.(\\|/)",
+    # Redirecting and used in release notes.
+    r"https://github\.com/nrfconnect/nrfxlib",
+    # Local preview URL used in examples.
+    "http://localhost:8000/latest/index.html",
+    # SES download links.
+    r"https://(www\.)?segger\.com/downloads/embedded-studio/embeddedstudio_arm_nordic_.+(_x\d+)?",
+    # Requires login.
+    "https://portal.azure.com/",
+    "https://threadgroup.atlassian.net/wiki/spaces/",
+    # Used as example in Doxygen.
+    "https://google.com:443",
+]
+
+linkcheck_anchors_ignore = [r"page="]
+linkcheck_timeout = 30
+linkcheck_retries = 2
+linkcheck_workers = 5