By default, the logo and links on an embedded Google Map accept tab focus. However, if the map is embedded in a form, you probably want tabbing to skip over the map since the map links have nothing to do with your form.
The easiest way is to wait until the map loads and then set the tabindex attributes to a high number, effectively disabling tab focus on the map.
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Tabindex could also be set to -1, but it’s technically not valid HTML5. Setting tabindex to a sufficiently high number works just fine.