bitbake: doc/bitbake-user-manual-intro: Mention existence of three supported "classes" directories

Early in Section 1, mention that BitBake supports three related
classes directories.

(Bitbake rev: 0d5201e904b0e6f4dd9f7bb116dda508ec09b78a)

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-intro.rst b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-intro.rst
index 98f152df80..d941e212bf 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-intro.rst
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-intro.rst
@@ -206,6 +206,18 @@ installing (empty by default) and packaging (empty by default). These
 tasks are often overridden or extended by other classes added during the
 project development process.
 
+.. note::
+
+   While BitBake comes with just the one ``base.bbclass`` file in the
+   ``classes`` directory, it supports class files also being installed
+   in related directories ``classes-global`` and ``classes-recipe`` and
+   will automatically search all three directories for a selected class
+   file.
+
+   This means that, in this documentation, when you see a reference to
+   class files being in the ``classes`` directory, you can interpret that
+   as meaning in any one of the above three directories.
+
 Layers
 ------