diff --git a/doc/develop/distro.rst b/doc/develop/distro.rst
index 8016aca..9e715b2 100644
--- a/doc/develop/distro.rst
+++ b/doc/develop/distro.rst
@@ -81,6 +81,12 @@
 * Does not document the fdtdir option, which automatically selects the DTB to
   pass to the kernel.
 
+* If no fdt/fdtdir is provided, the U-Boot will pass its own currently used
+  device tree.
+
+* If ``-`` is passed as fdt argument and ``CONFIG_SUPPORT_PASSING_ATAGS`` is
+  enabled, then no device tree will be used (legacy booting / pre-dtb kernel).
+
 See also doc/README.pxe under 'pxe file format'.
 
 One example extlinux.conf generated by the Fedora installer is::