Add an option to restore C-h b "Prefix Command" output

* lisp/help.el (describe-bindings-show-prefixes):  Option to enable prefixes.
(describe-map):  If true, restore "Prefix Command" output.
* etc/NEWS:  Describe the new option.

diff --git a/etc/NEWS b/etc/NEWS
index a5f9f8c6ec1..c4e16221d72 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -3563,6 +3563,10 @@ keymap descriptions have changed.  In particular, prefix commands are
 not output at all, and instead of "??" for closures/functions,
 "[closure]"/"[lambda]" is output.
 
+*** New user option 'describe-bindings-show-prefixes'.
+To reinstate the "Prefix Command" entries in key binding output for
+keys that are prefixes, set this option non-nil (the default is nil).
+
 ---
 ** 'downcase' details have changed slightly.
 In certain locales, changing the case of an ASCII-range character may
diff --git a/lisp/help.el b/lisp/help.el
index 83be85b1ee4..3e450fe0763 100644
--- a/lisp/help.el
+++ b/lisp/help.el
@@ -717,6 +717,12 @@ describe-bindings-outline
   :group 'help
   :version "29.1")
 
+(defcustom describe-bindings-show-prefixes nil
+  "Non-nil shows prefixes in the output buffer of `describe-bindings'."
+  :type 'boolean
+  :group 'help
+  :version "29.1")
+
 (declare-function outline-hide-subtree "outline")
 
 (defun describe-bindings (&optional prefix buffer)
@@ -1699,6 +1705,7 @@ describe-map
               (setq vect (cdr vect))
               (setq end (caar vect))))
           (when (or (not (eq start end))
+                    describe-bindings-show-prefixes
                     ;; Don't output keymap prefixes.
                     (not (keymapp definition)))
             (when first