[newlib-cygwin/main] Cygwin: doc: add note about raw devices of BitLocker partitions

[Christian Franke]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=4613a9a9799792a53444576de61bd1569f346ffa

commit 4613a9a9799792a53444576de61bd1569f346ffa
Author: Christian Franke <christian.franke@t-online.de>
Date:   Wed Jul 16 11:33:25 2025 +0200

    Cygwin: doc: add note about raw devices of BitLocker partitions
    
    Signed-off-by: Christian Franke <christian.franke@t-online.de>

Diff:
---
 winsup/doc/specialnames.xml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/winsup/doc/specialnames.xml b/winsup/doc/specialnames.xml
index 02375e737..4b232002a 100644
--- a/winsup/doc/specialnames.xml
+++ b/winsup/doc/specialnames.xml
@@ -361,6 +361,12 @@ the information between <filename>/proc/partitions</filename> and the
 <command>df</command> output, you should be able to figure out which
 external drive corresponds to which raw disk device name.</para>
 
+<para>Raw devices of partitions protected by BitLocker provide access to the
+<emphasis>decrypted</emphasis> NTFS image.  If the partition is locked, read
+attempts fail with <literal>Permission denied</literal>.  The corresponding
+block range from the raw device of the full disk provides access to the
+<emphasis>encrypted</emphasis> image as stored on the disk.</para>
+
 <note><para>Apart from tape devices which are not block devices and are
 by default accessed directly, accessing mass storage devices raw
 is something you should only do if you know what you're doing and know how to