Add README

Signed-off-by: Tobias Deiminger <tobias.deiminger@linutronix.de>

Author: haxtibal

README.md

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+# Exploring possibilities for integrating StrictDoc with ELISA’s requirements template approach for the Linux kernel
+
+This demonstrates how to realize the tool-agnostic
+[ELISA Kernel Requirements Template](https://docs.google.com/document/d/1c7S7YAledHP2EEQ2nh26Ibegij-XPNuUFkrFLtJPlzs/edit?tab=t.0)
+proposal by using [StrictDoc](https://strictdoc.readthedocs.io) as requirements processing tool. The repository contains a filtered (for brevity)
+copy of the Linux kernel with requirements and tests from Alessandro Carminat and Grabriele Paoloni ([^1], [^2]) applied on top. ELISA's
+[`SPDX-*` tagging scheme]((https://docs.google.com/document/d/1c7S7YAledHP2EEQ2nh26Ibegij-XPNuUFkrFLtJPlzs/edit?tab=t.0#heading=h.9dudo2y6dlhf))
+was [added](https://github.com/strictdoc-project/linux-strictdoc/commit/a876ef7671c4c17396b871643f46eb15c7afea73) along
+with a minimal StrictDoc project configuration.
+
+[^1]: https://lore.kernel.org/all/20250910170000.6475-1-gpaoloni@redhat.com/
+[^2]: https://lore.kernel.org/linux-trace-kernel/20250814122206.109096-1-gpaoloni@redhat.com/#r
+
+Go to [rendered requirements](https://strictdoc-project.github.io/linux-strictdoc/).
+
+#### Demonstrated features
+
+- Use `strictdoc export .` to generate a nice
+  [static HTML document tree](https://strictdoc-project.github.io/linux-strictdoc/linux-strictdoc/Documentation/requirements/charmisc.html)
+  with visual representation of the traceability graph, statistics, validation results and full-text search. Other
+  output formats as e.g. PDF are available.
+- Parses source code
+  [SPDX-Req-* tags proposed by ELISA](https://docs.google.com/document/d/1c7S7YAledHP2EEQ2nh26Ibegij-XPNuUFkrFLtJPlzs/edit?tab=t.0#heading=h.9dudo2y6dlhf)
+  and translates them to StrictDocs internal model.
+- Sidecar: Proposed by ELISA to hold additional requirement meta data outside source code. Realized as
+  [separate sdoc file](https://github.com/strictdoc-project/linux-strictdoc/blob/strictdoc/Documentation/requirements/tracing.sdoc)s
+  containing requirement stubs. Stubs are merged with source code tags by matching on `SPDX-Req-ID`.
+- Use `strictdoc manage auto-assign` to generate SPDX-Req-ID and SPDX-Req-HKey as suggested by Linux kernel 
+  requirements template. The hash generation method is `${PROJECT}${FILE_PATH}${INSTANCE}${CODE}" | sha256sum`. See
+  [commit 6a2952e8](https://github.com/strictdoc-project/linux-strictdoc/commit/6a2952e8)
+  for the auto-generated changes.
+- Tracing: Requirements, tests and functions become individual nodes in the traceability graph and are connected
+  by their stable IDs.
+- Custom validations: Use plugin API to
+  [provide a check](https://github.com/strictdoc-project/linux-strictdoc/blob/strictdoc/tools/requirements/validation_plugin.py#L28)
+  to see if each requirement has at least one associated test, and each function expectations has at least one dedicated 
+  test. 
+- Drift detection: As kernel development goes on, occasionally rerun `strictdoc manage auto-assign`. If `SPDX-Req-HKey`
+  changes, this means that some semantic aspect of the requirement may have changed. 
+
+For a thorough documentation of StrictDocs features see
+[StrictDoc User Guide ](https://strictdoc.readthedocs.io/en/stable/stable/docs/strictdoc_01_user_guide.html)
+
+#### Usage
+
+```sh
+pipx install strictdoc
+git clone https://github.com/strictdoc-project/linux-strictdoc
+cd linux-strictdoc
+strictdoc export .           # validate and render to HTML
+strictdoc manage auto-uid .  # regenerate hashes for drift detection
+```
+
+#### Explanation of Content and Processing
+
+```
+.
+├── Documentation
+│         └── requirements
+│             ├── charmisc.sdoc         # side-car
+│             └── tracing.sdoc          # side-car
+├── drivers
+│         └── char
+│             └── mem.c                 # Linux code with inlined LLRs
+├── kernel
+│         └── trace
+│             └── trace_events.c        # Linux code with inlined LLRs
+├── strictdoc_config.py                 # StrictDoc project configuration
+└── tools
+    ├── requirements
+    │         └── validation_plugin.py  # custom requirement validations
+    └── testing
+        └── selftests
+            └── devmem
+                      └── tests.c       # tests for /dev/mem LLRs
+```
+
+StrictDoc performs the following notable process steps:
+- parse \*.sdoc files to create the initial traceability index (a DAG structure) 
+- parse \*.c files using tree-sitter, read SPDX tags from it and merge it into the DAG
+- perform built-in validations and calculate built-in statistics
+- perform custom validations
+  * check if all requirements have at least one related test
+  * check if all function expectations are mentioned by one related test
+- render the DAG into a HTML document tree where all nodes are traceable, including
+  requirements text, visual graph representation and source code view