Computer Configuration > Administrative Templates > Google Chrome > Content settings
Both
HKLM\Software\Policies\Google\Chrome
Setting the policy lets you list the URL patterns that specify which sites can't ask users to grant them access to a serial port. Leaving the policy unset means DefaultSerialGuardSetting applies for all sites, if it's set. If not, the user's personal setting applies. For URL patterns which do not match the policy SerialAskForUrls (if there is a match), DefaultSerialGuardSetting (if set), or the users' personal settings take precedence, in that order. If URL patterns conflict with SerialAskForUrls this policy will take precedence. For detailed information on valid url patterns, please see https://cloud.google.com/docs/chrome-enterprise/policies/url-patterns. * is not an accepted value for this policy. Example value: https://www.example.com [*.]example.edu