Hello @Lubos Dvorak Usually the request is onprem to online migration which Commvault has an entire migration option available 

https://documentation.commvault.com/11.24/expert/92416_migrating_sharepoint_on_premise_data_to_office_365_site_01.html

However you can still restore online to onprem you would need to configure a Sharepoint agent for both the online and onprem then restore out of place. You can also restore data to a disk location as native sharepoint files or actual files and import then in Sharepoint

https://documentation.commvault.com/11.24/expert/17976_restoring_documents_to_disk.html