The Product Owner has to understand that planning is adaptive, iterative, and collaborative which means, planning takes place at DIFFERENT levels in Scrum: 

Product, release, sprint, and day. Each level has some output which gets as an input for the next level. When we talk of planning in Scrum, it is more dynamic and change as more information about the customer needs and the product being DEVELOPED becomes AVAILABLE. The product gets build over every iteration, at the end of every sprint, there is an increment which gets ADDED to the product. The team plans for each iteration in a release with the collaboration of the product owner and the stakeholders. 

The release planning activities are carried out by the Scrum team often with the help of stakeholders, for instance, in the sprint review meeting, the team presents the backlog they have worked UPON and take the acceptance from the product owner. If there is any feedback on the items, it will be added in the product backlog and later would be prioritized by the product owner. The product owner ensures that the necessary release management activities take place. It is more of a collaboration among the product owner and the teams which results in the success of the product.