Add initial API doc configuration

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/docs/conf.py b/docs/conf.py
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--- /dev/null
+++ b/docs/conf.py
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+# Configuration file for the Sphinx documentation builder.
+#
+# For the full list of built-in configuration values, see the documentation:
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
+
+# -- Project information -----------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
+import glob
+
+project = 'Mbed TLS Versioned'
+copyright = '2023, Mbed TLS Contributors'
+author = 'Mbed TLS Contributors'
+
+# -- General configuration ---------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration
+
+extensions = ['breathe', 'sphinx.ext.graphviz']
+
+templates_path = ['_templates']
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
+
+breathe_projects = {
+    'mbedtls-versioned': '../apidoc/xml'
+}
+breathe_default_project = 'mbedtls-versioned'
+
+primary_domain = 'c'
+highlight_language = 'c'
+
+# -- Options for HTML output -------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
+
+html_theme = 'sphinx_rtd_theme'
+html_static_path = ['_static']