[{_id:1,lodging:{reviews:[{cleanliness:0,location:0,food:2},{cleanliness:3,location:4,food:5}]}},{_id:2,lodging:{reviews:[{cleanliness:5,location:5,food:5}]}}]

db.collection.aggregate([{"$addFields":{"sumPoints":{$sum:[{$sum:["$lodging.reviews.cleanliness"]},{$sum:["$lodging.reviews.location"]},{$sum:["$lodging.reviews.food"]}]}}}])