Wi-Fi: Add roaming support (802.11k,v,r)

Useful feature if running multiple radios on single AP with
the same SSIDs or multiple APs to get good area coverage.

doc/wifi.md

@@ -486,6 +486,101 @@ radio settings, and `show interface` to see all active AP interfaces.
 > AP and Station modes cannot be mixed on the same radio. All virtual interfaces
 > on a radio must be the same mode (all APs or all Stations).
 
+## Fast Roaming Between Access Points
+
+Fast roaming enables seamless client handoff between access points through
+802.11k/r/v standards. These features can be enabled individually based on
+your requirements.
+
+### 802.11r - Fast BSS Transition
+
+Enable 802.11r for fast handoff (<50ms) between APs with the same SSID:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r mobility-domain 4f57
+```
+
+**Requirements:**
+- All APs in roaming group must have **identical** SSID
+- All APs must have **identical** passphrase (same keystore secret)
+- All APs must use the **same mobility-domain** identifier
+
+**Mobility Domain Options:**
+- Explicit 4-character hex value (e.g., `4f57`) - default if not specified
+- `hash` - Automatically derive from SSID using MD5 (OpenWrt-compatible)
+
+Using `hash` allows multiple APs with the same SSID to automatically share
+the same mobility domain without manual configuration:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r mobility-domain hash
+```
+
+You can optionally set NAS identifier mode:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r nas-identifier auto
+```
+
+`auto` derives:
+
+`<interface-name>-<hostname>.<mobility-domain>`
+
+Or set an explicit string:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r nas-identifier ap01.wifi0.4f57
+```
+
+### 802.11k - Radio Resource Management
+
+Enable 802.11k for client neighbor discovery and better roaming decisions:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11k
+```
+
+Enables neighbor reports and beacon reports, allowing clients to discover
+nearby APs before roaming.
+
+### 802.11v - BSS Transition Management
+
+Enable 802.11v for network-assisted roaming:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11v
+```
+
+Allows APs to suggest better APs to clients, improving roaming decisions.
+
+### Recommended Configuration
+
+For optimal roaming experience, enable all three features:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11k
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11v
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r mobility-domain 4f57
+```
+
+Or use `hash` for automatic mobility domain derivation from SSID:
+
+```
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11k
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11v
+admin@example:/config/interface/wifi0/> set wifi access-point roaming dot11r mobility-domain hash
+```
+
+Repeat for all APs that should participate in the roaming group.
+
+> [!NOTE]
+> Not all client devices support all roaming features. Modern devices typically
+> support 802.11k/r/v, but older devices may only support basic roaming without
+> fast transition.
+
 ### AP as Bridge Port
 
 WiFi AP interfaces can be added to bridges to integrate wireless devices