diff --git a/tools/normalise_mpconfigport.py b/tools/normalise_mpconfigport.py
new file mode 100644
index 0000000000000..9439d229b4daa
--- /dev/null
+++ b/tools/normalise_mpconfigport.py
@@ -0,0 +1,75 @@
+"""
+Normalise an mpconfigport.h file by ordering config options, and removing any
+that are the defaults.  The standard order and defaults come from py/mpconfig.h.
+
+Run from the root of the repository.
+
+Example usage:
+
+    python3 tools/normalise_mpconfigport.py ports/stm32/mpconfigport.h
+
+"""
+
+import collections, re, sys
+
+
+regexs = (
+    ("define", re.compile(r"#define (MICROPY_[A-Z0-9_]+) +(.+)")),
+    ("comment", re.compile(r"// (Extended modules)")),
+    ("comment_strip", re.compile(r"/\* (.+) \*/")),
+)
+
+
+def match_line(line):
+    for kind, regex in regexs:
+        m = regex.match(line)
+        if m:
+            return kind, m
+    return None, None
+
+
+def parse_config(filename, parse_section_names=False):
+    config = collections.OrderedDict()
+    section_num = 0
+    section_comment = None
+    with open(filename) as f:
+        for line in f:
+            kind, match = match_line(line)
+            if kind == "define":
+                if section_comment:
+                    if parse_section_names:
+                        config[f"_section{section_num}"] = section_comment
+                    section_num += 1
+                    section_comment = None
+                config[match.group(1)] = match.group(2)
+            elif kind == "comment":
+                section_comment = match.group(1)
+            elif kind == "comment_strip":
+                section_comment = match.group(1).strip()
+
+    return config
+
+
+def main():
+    defaults = parse_config("py/mpconfig.h", True)
+    port = parse_config(sys.argv[1])
+
+    # Print out the standard config options in order.
+    for k, v in defaults.items():
+        if k.startswith("_section"):
+            print()
+            print(f"// {v}")
+            continue
+        if k in port:
+            if port[k] != v:
+                print("#define {:40}{}".format(k, port[k]))
+            del port[k]
+
+    # Print out any remaining config options that are not standard ones.
+    if port:
+        print()
+        for k, v in port.items():
+            print("#define {:40}{}".format(k, v))
+
+
+main()