kconfig: Document automatic submenu creation code

		for (menu = parent->list; menu; menu = menu->next)

			menu_finalize(menu);

	} else if (sym) {

		/*

		 * Automatic submenu creation. If sym is a symbol and A, B, C,

		 * ... are consecutive items (symbols, menus, ifs, etc.) that

		 * all depend on sym, then the following menu structure is

		 * created:

		 *

		 *	sym

		 *	 +-A

		 *	 +-B

		 *	 +-C

		 *	 ...

		 *

		 * This also works recursively, giving the following structure

		 * if A is a symbol and B depends on A:

		 *

		 *	sym

		 *	 +-A

		 *	 | +-B

		 *	 +-C

		 *	 ...

		 */

		basedep = parent->prompt ? parent->prompt->visible.expr : NULL;

		basedep = expr_trans_compare(basedep, E_UNEQUAL, &symbol_no);

		basedep = expr_eliminate_dups(expr_transform(basedep));

		/* Examine consecutive elements after sym */

		last_menu = NULL;

		for (menu = parent->next; menu; menu = menu->next) {

			dep = menu->prompt ? menu->prompt->visible.expr : menu->dep;

			if (!expr_contains_symbol(dep, sym))

				/* No dependency, quit */

				break;

			if (expr_depends_symbol(dep, sym))

				/* Absolute dependency, put in submenu */

				goto next;

			/*

			 * Also consider it a dependency on sym if our

			 * dependencies contain sym and are a "superset" of

			 * sym's dependencies, e.g. '(sym || Q) && R' when sym

			 * depends on R.

			 *

			 * Note that 'R' might be from an enclosing menu or if,

			 * making this a more common case than it might seem.

			 */

			dep = expr_trans_compare(dep, E_UNEQUAL, &symbol_no);

			dep = expr_eliminate_dups(expr_transform(dep));

			dep2 = expr_copy(basedep);

			expr_eliminate_eq(&dep, &dep2);

			expr_free(dep);

			if (!expr_is_yes(dep2)) {

				/* Not superset, quit */

				expr_free(dep2);

				break;

			}

			/* Superset, put in submenu */

			expr_free(dep2);

		next:

			menu_finalize(menu);