def rscpFindTag(decodedMsg, tag):
    """Finds a submessage with a specific tag.

    Args:
    decodedMsg (list): the decoded message
    tag (str): the RSCP Tag string to search for

    Returns:
        list: the found tag
    """
    if decodedMsg is None:
        return None
    if decodedMsg[0] == tag:
        return decodedMsg
    if isinstance(decodedMsg[2], list):
        for msg in decodedMsg[2]:
            msgValue = rscpFindTag(msg, tag)
            if msgValue is not None:
                return msgValue
    return None