doc: maintaining nghttp2

PR-URL: https://github.com/nodejs/node/pull/46539
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

doc/contributing/maintaining-http.md

@@ -113,11 +113,6 @@ directory and C++ code in the
 
 The low-level implementation of
 [HTTP2](https://nodejs.org/docs/latest/api/http2.html)
-is based on [nghttp2](https://nghttp2.org/). Updates are pulled into Node.js
-under [deps/nghttp2](https://github.com/nodejs/node/tree/HEAD/deps/nghttp2)
-as needed.
+is based on [nghttp2](https://nghttp2.org/). See [maintaining nghttp2][].
 
-The low-level implementation is made available in the Node.js API through
-JavaScript code in the [lib](https://github.com/nodejs/node/tree/HEAD/lib)
-directory and C++ code in the
-[src](https://github.com/nodejs/node/tree/HEAD/src) directory.
+[maintaining nghttp2]: ./maintaining-nghttp2.md

doc/contributing/maintaining-nghttp2.md

@@ -0,0 +1,46 @@
+# Maintaining nghttp2 in Node.js
+
+The low-level implementation of
+[HTTP2](https://nodejs.org/docs/latest/api/http2.html)
+is based on [nghttp2](https://nghttp2.org/). Updates are pulled into Node.js
+under [deps/nghttp2](https://github.com/nodejs/node/tree/HEAD/deps/nghttp2)
+as needed.
+
+The low-level implementation is made available in the Node.js API through
+JavaScript code in the [lib](https://github.com/nodejs/node/tree/HEAD/lib)
+directory and C++ code in the
+[src](https://github.com/nodejs/node/tree/HEAD/src) directory.
+
+## Step 1: Updating nghttp2
+
+The `tools/update-nghttp2.sh` script automates the update of the
+postject source files.
+
+In the following examples, `x.y.z` should match the nghttp2
+version to update to.
+
+```console
+$ ./tools/update-nghttp2.sh x.y.z
+```
+
+## Step 2: Test the build
+
+```console
+$  make test-http2
+```
+
+## Step 3: Commit new nghttp2
+
+```console
+$ git add -A deps/nghttp2
+$ git commit -m "deps: upgrade nghttp2 to x.y.z"
+```
+
+## Step 4: Update licenses
+
+```console
+$ ./tools/license-builder.sh
+# The following commands are only necessary if there are changes
+$ git add .
+$ git commit -m "doc: update nghttp2 LICENSE using license-builder.sh"
+```