[5.2.x] Fixed #17461 -- Doc'd the presumed order of foreign keys on the intermediary model of a self-referential m2m.

Thanks Giannis Terzopoulos and Sarah Boyce for the reviews.

Backport of 9d93e35c207a001de1aa9ca9165bdec824da9021 from main.

1 files changed, 6 insertions, 3 deletions

diff --git a/docs/topics/db/models.txt b/docs/topics/db/models.txt
index 98fb149b98..14233cbefd 100644
--- a/docs/topics/db/models.txt
+++ b/docs/topics/db/models.txt
@@ -533,9 +533,12 @@ There are a few restrictions on the intermediate model:
 * For a model which has a many-to-many relationship to itself through an
   intermediary model, two foreign keys to the same model are permitted, but
   they will be treated as the two (different) sides of the many-to-many
-  relationship. If there are *more* than two foreign keys though, you
-  must also specify ``through_fields`` as above, or a validation error
-  will be raised.
+  relationship. If :attr:`~.ManyToManyField.through_fields` is not specified,
+  the first foreign key will be taken to represent the source side of the
+  ``ManyToManyField``, while the second will be taken to represent the target
+  side. If there are *more* than two foreign keys though, you must specify
+  :attr:`~.ManyToManyField.through_fields` to explicitly indicate which foreign
+  keys to use, otherwise a validation error will be raised.
 
 Now that you have set up your :class:`~django.db.models.ManyToManyField` to use
 your intermediary model (``Membership``, in this case), you're ready to start