Update documentations describing startup mode

Author: PatrickRen

docs/content/connectors/mysql-cdc.md

@@ -218,10 +218,30 @@ Connector Options
       <td>optional</td>
       <td style="word-wrap: break-word;">initial</td>
       <td>String</td>
-      <td>Optional startup mode for MySQL CDC consumer, valid enumerations are "initial"
-           and "latest-offset". 
-           Please see <a href="#startup-reading-position">Startup Reading Position</a>section for more detailed information.</td>
-    </tr> 
+      <td>Optional startup mode for MySQL CDC consumer, valid enumerations are "initial"，"earliest-offset", "latest-offset", "specific-offset" and "timestamp".
+           Please see <a href="#startup-reading-position">Startup Reading Position</a> section for more detailed information.</td>
+    </tr>
+    <tr>
+      <td>scan.startup.specific-offset.file</td>
+      <td>optional</td>
+      <td style="word-wrap: break-word;">(none)</td>
+      <td>String</td>
+      <td>Optional binlog file name used in case of "specific-offset" startup mode</td>
+    </tr>
+    <tr>
+      <td>scan.startup.specific-offset.pos</td>
+      <td>optional</td>
+      <td style="word-wrap: break-word;">(none)</td>
+      <td>Long</td>
+      <td>Optional GTID set used in case of "specific-offset" startup mode</td>
+    </tr>
+    <tr>
+      <td>scan.startup.specific-offset.gtid-set</td>
+      <td>optional</td>
+      <td style="word-wrap: break-word;">(none)</td>
+      <td>Long</td>
+      <td>Optional binlog file position used in case of "specific-offset" startup mode</td>
+    </tr>
     <tr>
       <td>server-time-zone</td>
       <td>optional</td>
@@ -527,10 +547,15 @@ both snapshot phase and binlog phase, MySQL CDC connector read with **exactly-on
 The config option `scan.startup.mode` specifies the startup mode for MySQL CDC consumer. The valid enumerations are:
 
 - `initial` (default): Performs an initial snapshot on the monitored database tables upon first startup, and continue to read the latest binlog.
+- `earliest-offset`: Skip snapshot phase and start reading binlog events from the earliest accessible binlog offset.
 - `latest-offset`: Never to perform snapshot on the monitored database tables upon first startup, just read from
 the end of the binlog which means only have the changes since the connector was started.
+- `specific-offset`: Skip snapshot phase and start reading binlog events from a specific offset. The offset could be
+specified with binlog filename and position, or a GTID set if GTID is enabled on server.
+- `timestamp`: Skip snapshot phase and start reading binlog events from a specific timestamp.
 
-_Note: the mechanism of `scan.startup.mode` option relying on Debezium's `snapshot.mode` configuration. So please do not using them together. If you speicifying both `scan.startup.mode` and `debezium.snapshot.mode` options in the table DDL, it may make `scan.startup.mode` doesn't work._
+**Note:** MySQL source will print the current binlog position into logs with INFO level on checkpoint, with the prefix
+"Binlog offset on checkpoint {checkpoint-id}". It could be useful if you want to restart the job from a specific checkpointed position.
 
 ### DataStream Source