doc/sphinx: fix Python string escapes

Python 3.6 introduced a DeprecationWarning for invalid escape sequences.
This is upgraded to a SyntaxWarning in Python 3.12, and will eventually
be a syntax error.

Fix these now to get ahead of it before it's an error.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Message-ID: <20230912060801.95533-3-bgray@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Adapted for U-Boot
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/sphinx/maintainers_include.py b/doc/sphinx/maintainers_include.py
index dc8fed4..6cee52c 100755
--- a/doc/sphinx/maintainers_include.py
+++ b/doc/sphinx/maintainers_include.py
@@ -79,7 +79,7 @@
             line = line.rstrip()
 
             # Linkify all non-wildcard refs to ReST files in Documentation/.
-            pat = '(Documentation/([^\s\?\*]*)\.rst)'
+            pat = r'(Documentation/([^\s\?\*]*)\.rst)'
             m = re.search(pat, line)
             if m:
                 # maintainers.rst is in a subdirectory, so include "../".
@@ -92,11 +92,11 @@
                 output = "| %s" % (line.replace("\\", "\\\\"))
                 # Look for and record field letter to field name mappings:
                 #   R: Designated *reviewer*: FullName <address@domain>
-                m = re.search("\s(\S):\s", line)
+                m = re.search(r"\s(\S):\s", line)
                 if m:
                     field_letter = m.group(1)
                 if field_letter and not field_letter in fields:
-                    m = re.search("\*([^\*]+)\*", line)
+                    m = re.search(r"\*([^\*]+)\*", line)
                     if m:
                         fields[field_letter] = m.group(1)
             elif subsystems:
@@ -114,7 +114,7 @@
                     field_content = ""
 
                     # Collapse whitespace in subsystem name.
-                    heading = re.sub("\s+", " ", line)
+                    heading = re.sub(r"\s+", " ", line)
                     output = output + "%s\n%s" % (heading, "~" * len(heading))
                     field_prev = ""
                 else: