[PATCH] readlinkat: document GNU/Linux "" divergence

---
 doc/posix-functions/readlinkat.texi | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/doc/posix-functions/readlinkat.texi b/doc/posix-functions/readlinkat.texi
index 0d664437a5..ed362fbb43 100644
--- a/doc/posix-functions/readlinkat.texi
+++ b/doc/posix-functions/readlinkat.texi
@@ -44,6 +44,15 @@ readlinkat
 Portability problems not fixed by Gnulib:
 @itemize
 @item
+Behaviors differ when this function is called on an empty file name.
+On most platforms, the function fails with error @code{ENOENT}.
+On Cygnus 3.4.6, the function fails with error @code{EBADF} instead.
+@c https://cygwin.com/pipermail/cygwin/2023-April/253510.html
+On GNU/Linux (kernel version 2.6.39 or later), when @var{dirfd} is
+nonnegative the function instead reads directly from @var{dirfd},
+and this succeeds if @var{dirfd} corresponds to a symbolic link that
+was opened with @code{O_PATH | O_NOFOLLOW}.
+@item
 This function always fails on platforms that don't support symlinks:
 mingw, MSVC 14.
 @item
@@ -60,11 +69,6 @@ readlinkat
 it sets @code{errno} to @code{EINVAL}:
 AIX 7.2.
 @item
-When this function is called on an empty file name, it fails with error
-@code{EBADF} instead of @code{ENOENT}:
-@c https://cygwin.com/pipermail/cygwin/2023-April/253510.html
-Cygwin 3.4.6.
-@item
 Symlink contents do not always have a trailing null byte, and there is
 no indication if symlink contents were truncated if the return value
 matches the length.  Furthermore,
-- 
2.54.0