Short summary, RouterOS implementation of an IEEE 802.1BR standard, description of a Controller Bridge and Port Extender, description of a cascade, control (and upstream), extended ports (image), table of supported devices and features.
Quick setup (optional)
Short quick-setup with configuration (image)
Packet flow and forwarding
ETAG usage, packet flooding (broadcast, multicast, unicast), unicast forwarding, learning.
Controller Bridge settings
List of available configuration properties, monitoring options. Neighbor discovery changes (how PE and CB discover each other using LLDP TLVs, on PE control-ports discovery is automatically enabled and disabled on extended ports (they get controlled by the CB settings), on CB cascade ports discovery is automatically enabled), automatic bridge port configuration, how to apply and remove (device remove, port remove, other settings where an extended interface is configured will stay and should be removed manually) the configuration for extender ports (PE can even be disconnected and still apply configuration on CB), extended port naming, ECP protocol for control information between PE and CB.
Port Extender settings
Similar as CB
Known limitation (e.g. only single CB possible, ingress-filtering on extended ports) and recommendations (e.g use control/cascade ports only for communication between CB and PE, do not use these ports for bridging or routing)
Some most basic and commonly used examples