cmd X - like messages are from SPA112 kernel syslog - they are not useful most of time. For the purpose of SIP issues debugging you need to capture VoiceApplication syslog messages (those are NOT captured internally by SPA112, they are sent to external syslog server only). Those are less cryptic and someone familiar with SIP protocol can interpret meaning of most of them. But short answer is "no, there's no documentation related to those messages, Cisco doesn't support self-service, buy support contract instead".
... View more