sphinx.rst: better organize the documentation about PDF build

Instead of having it on just one note, add a separate section.

This way, we could later improve it, providing a better
guide about the needed steps for PDF builds.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/doc-guide/sphinx.rst

@@ -60,14 +60,6 @@ in order to indicate that you're using the new environment. If you
 open a new shell, you need to rerun this command to enter again at
 the virtual environment before building the documentation.
 
-.. note::
-
-  Please notice that, for PDF and LaTeX output, you'll also need ``XeLaTeX``
-  version 3.14159265. Depending on the distribution, you may also need to
-  install a series of ``texlive`` packages that provide the minimal set of
-  functionalities required for ``XeLaTex`` to work. For PDF output you'll also
-  need ``convert(1)`` from ImageMagick (https://www.imagemagick.org).
-
 Image output
 ------------
 
@@ -80,6 +72,19 @@ packages. If those packages are not installed, the build system will
 still build the documentation, but won't include any images at the
 output.
 
+PDF and LaTeX builds
+--------------------
+
+Such builds are currently supported only with Sphinx versions 1.4 and 1.5.
+
+Currently, it is not possible to do pdf builds with Sphinx version 1.6.
+
+For PDF and LaTeX output, you'll also need ``XeLaTeX`` version 3.14159265.
+
+Depending on the distribution, you may also need to install a series of
+``texlive`` packages that provide the minimal set of functionalities
+required for ``XeLaTex`` to work.
+
 Sphinx Build
 ============