Together with the new BT5 advertising APIs introduced in SDK 2.3.x there was also a new event introduced le_gap_scan_request to notify the application that a scan request has been received.
The BT5 API le_gap_bt5_set_adv_parameters has one parameter called report_scan which will enable scan request reporting via le_gap_scan_request every time that a scan request is received.
The le_gap_scan_request event will inform the application of what is the Bluetooth address (and address type) as well as bonding status of the device that sent the scan request.
From SDK 2.8.0 the API le_gap_bt5_set_adv_parameters has been deprecated. To enable scan request reporting a new API was introduced le_gap_set_advertise_report_scan_request. The event that signals a scan request remains the same.
Note: For a more complete mapping between the deprecated and new APIs please refer to the following KBA: