doc: add note about stdio streams in child_process

PR-URL: #55322
Fixes: #15714
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/child_process.md

@@ -1061,6 +1061,15 @@ pipes between the parent and child. The value is one of the following:
    corresponds to the index in the `stdio` array. The stream must have an
    underlying descriptor (file streams do not start until the `'open'` event has
    occurred).
+   **NOTE:** While it is technically possible to pass `stdin` as a writable or
+   `stdout`/`stderr` as readable, it is not recommended.
+   Readable and writable streams are designed with distinct behaviors, and using
+   them incorrectly (e.g., passing a readable stream where a writable stream is
+   expected) can lead to unexpected results or errors. This practice is discouraged
+   as it may result in undefined behavior or dropped callbacks if the stream
+   encounters errors. Always ensure that `stdin` is used as writable and
+   `stdout`/`stderr` as readable to maintain the intended flow of data between
+   the parent and child processes.
 7. Positive integer: The integer value is interpreted as a file descriptor
    that is open in the parent process. It is shared with the child
    process, similar to how {Stream} objects can be shared. Passing sockets