doc: move README.menu to HTML documentation

Convert README.menu to reStructured text and add it to the HTML
documentation.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/doc/develop/index.rst b/doc/develop/index.rst
index 83eb130..beaa64d 100644
--- a/doc/develop/index.rst
+++ b/doc/develop/index.rst
@@ -12,6 +12,7 @@
    commands
    global_data
    logging
+   menus
 
 Debugging
 ---------
diff --git a/doc/develop/menus.rst b/doc/develop/menus.rst
new file mode 100644
index 0000000..dda8f96
--- /dev/null
+++ b/doc/develop/menus.rst
@@ -0,0 +1,131 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright 2010-2011 Calxeda, Inc.
+
+Menus
+=====
+
+U-Boot provides a set of interfaces for creating and using simple, text
+based menus. Menus are displayed as lists of labeled entries on the
+console, and an entry can be selected by entering its label.
+
+To use the menu code, enable CONFIG_MENU, and include "menu.h" where
+the interfaces should be available.
+
+Menus are composed of items. Each item has a key used to identify it in
+the menu, and an opaque pointer to data controlled by the consumer.
+
+If you want to show a menu, instead starting the shell, define
+CONFIG_AUTOBOOT_MENU_SHOW. You have to code the int menu_show(int bootdelay)
+function, which handle your menu. This function returns the remaining
+bootdelay.
+
+Interfaces
+----------
+
+.. code-block:: c
+
+    #include "menu.h"
+
+    /*
+     * Consumers of the menu interfaces will use a struct menu * as the
+     * handle for a menu. struct menu is only fully defined in menu.c,
+     * preventing consumers of the menu interfaces from accessing its
+     * contents directly.
+     */
+    struct menu;
+
+    /*
+     * NOTE: See comments in common/menu.c for more detailed documentation on
+     * these interfaces.
+     */
+
+    /*
+     * menu_create() - Creates a menu handle with default settings
+     */
+    struct menu *menu_create(char *title, int timeout, int prompt,
+                             void (*item_data_print)(void *),
+                             char *(*item_choice)(void *),
+                             void *item_choice_data);
+
+    /*
+     * menu_item_add() - Adds or replaces a menu item
+     */
+    int menu_item_add(struct menu *m, char *item_key, void *item_data);
+
+    /*
+     * menu_default_set() - Sets the default choice for the menu
+     */
+    int menu_default_set(struct menu *m, char *item_key);
+
+    /*
+     * menu_default_choice() - Set *choice to point to the default item's data
+     */
+    int menu_default_choice(struct menu *m, void **choice);
+
+    /*
+     * menu_get_choice() - Returns the user's selected menu entry, or the
+     * default if the menu is set to not prompt or the timeout expires.
+     */
+    int menu_get_choice(struct menu *m, void **choice);
+
+    /*
+     * menu_destroy() - frees the memory used by a menu and its items.
+     */
+    int menu_destroy(struct menu *m);
+
+    /*
+     * menu_display_statusline(struct menu *m);
+     * shows a statusline for every menu_display call.
+     */
+    void menu_display_statusline(struct menu *m);
+
+Example Code
+------------
+
+This example creates a menu that always prompts, and allows the user
+to pick from a list of tools.  The item key and data are the same.
+
+.. code-block:: c
+
+    #include "menu.h"
+
+    char *tools[] = {
+        "Hammer",
+        "Screwdriver",
+        "Nail gun",
+        NULL
+    };
+
+    char *pick_a_tool(void)
+    {
+        struct menu *m;
+        int i;
+        char *tool = NULL;
+
+        m = menu_create("Tools", 0, 1, NULL);
+
+        for(i = 0; tools[i]; i++) {
+            if (menu_item_add(m, tools[i], tools[i]) != 1) {
+                printf("failed to add item!");
+                menu_destroy(m);
+                return NULL;
+            }
+        }
+
+        if (menu_get_choice(m, (void **)&tool) != 1)
+            printf("Problem picking tool!\n");
+
+        menu_destroy(m);
+
+        return tool;
+    }
+
+    void caller(void)
+    {
+        char *tool = pick_a_tool();
+
+        if (tool) {
+            printf("picked a tool: %s\n", tool);
+            use_tool(tool);
+        }
+    }