[PATCH v7 15/17] docs: sphinx: add a file with the requirements for lowest version

Those days, it is hard to install a virtual env that would
build docs with Sphinx 3.4.3, as even python 3.13 is not
compatible anymore with it.

	/usr/bin/python3.9 -m venv sphinx_3.4.3
	. sphinx_3.4.3/bin/activate
	pip install -r Documentation/sphinx/min_requirements.txt

Signed-off-by: Mauro Carvalho Chehab <[email protected]>
---
 Documentation/doc-guide/sphinx.rst        | 15 +++++++++++++++
 Documentation/sphinx/min_requirements.txt |  8 ++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 Documentation/sphinx/min_requirements.txt

diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst
index 5a91df105141..13943eb532ac 100644
--- a/Documentation/doc-guide/sphinx.rst
+++ b/Documentation/doc-guide/sphinx.rst
@@ -131,6 +131,21 @@ It supports two optional parameters:
 ``--no-virtualenv``
 	Use OS packaging for Sphinx instead of Python virtual environment.
 
+Installing Sphinx Minimal Version
+---------------------------------
+
+When changing Sphinx build system, it is important to ensure that
+the minimal version will still be supported. Nowadays, it is
+becoming harder to do that on modern distributions, as it is not
+possible to install with Python 3.13 and above.
+
+The recommended way is to use the lowest supported Python version
+as defined at Documentation/process/changes.rst, creating
+a venv with it with, and install minimal requirements with::
+
+	/usr/bin/python3.9 -m venv sphinx_min
+	. sphinx_min/bin/activate
+	pip install -r Documentation/sphinx/min_requirements.txt
 
 Sphinx Build
 ============
diff --git a/Documentation/sphinx/min_requirements.txt b/Documentation/sphinx/min_requirements.txt
new file mode 100644
index 000000000000..89ea36d5798f
--- /dev/null
+++ b/Documentation/sphinx/min_requirements.txt
@@ -0,0 +1,8 @@
+Sphinx==3.4.3
+jinja2<3.1
+docutils<0.18
+sphinxcontrib-applehelp==1.0.4
+sphinxcontrib-devhelp==1.0.2
+sphinxcontrib-htmlhelp==2.0.1
+sphinxcontrib-qthelp==1.0.3
+sphinxcontrib-serializinghtml==1.1.5
-- 
2.49.0