In the latest update of Google Maps released today, the company has added a feature to mark your parking spot and share it with friends,

If you open up the app and tap the blue location dot, you'll see a new option to "Set as parking location" (iOS) or "Save your parking" (Android). Once that's selected, you'll see the classic little "P" icon appear on the map, and tapping on that brings up a host of new options

http://www.thedrive.com/tech/9698/google-maps-adds-feature-that-reminds-you-where-you-parked