trivial: Add some additional docs about CCGX factory mode

plugins/ccgx/README.md

@@ -56,6 +56,36 @@ The `CY_PD_JUMP_TO_ALT_FW_CMD_SIG` command is allowed only in asymmetric FW, but
 In composite firmware topology, a single firmware image contains metadata and
 firmware images of multiple devices including DMC itself in a dock system.
 
+### DMC Factory Mode
+
+Dock Management Controller devices have a *composite version* that is used to
+describe the dock hardware as a whole, rather than enumerating and updating
+each sub-component separately.
+When OEMs have not followed the IHV-approved factory assembly process, the
+composite number is unset and fwupd would display `0.0.0.0` in the GUI and
+on the command line.
+
+In fwupd >= 1.8.11 we detect if the device is in *factory mode* and set the
+version number to `0.0.0.1`.
+When the device is in factory mode any valid upgrade will be allowed, which
+means the user might be prompted to “update to” the same current version
+installed on the dock.
+For millions of devices this is both a waste of time, resources, and also
+would inconvenience the user with an additional process for no reason.
+
+For devices that have been shipped in factory mode, but would like to avoid
+the update from `0.0.0.1` to the original version on the LVFS, can add a
+quirk entry which matches the `devx` subcomponent *base version*.
+In this example we match the parent VID, PID, the ComponentID and the `devx`
+base firmware version, setting the parent composite version to `0.0.0.15`.
+
+    [USB\VID_2188&PID_0035&CID_05&VER_3.3.1.69]
+    CcgxDmcCompositeVersion = 15
+
+All the `devx` subcomponent versions can be shown on the console using:
+
+    sudo fwupdtool –plugins ccgx get-devices –show-all –verbose
+
 ## Firmware Format
 
 There are two kinds of firmware format.