Add documentation

Firmware/Marlin_main.cpp

@@ -3734,6 +3734,7 @@ extern uint8_t st_backlash_y;
 //!@n M503 - print the current settings (from memory not from EEPROM)
 //!@n M509 - force language selection on next restart
 //!@n M540 - Use S[0|1] to enable or disable the stop SD card print on endstop hit (requires ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
+//!@n M552 - Set IP address
 //!@n M600 - Pause for filament change X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]
 //!@n M605 - Set dual x-carriage movement mode: S<mode> [ X<duplication x-offset> R<duplication temp offset> ]
 //!@n M860 - Wait for PINDA thermistor to reach target temperature.
@@ -8005,6 +8006,19 @@ Sigma_Exit:
       break;
     }
     #endif // CUSTOM_M_CODE_SET_Z_PROBE_OFFSET
+
+	/*!
+	### M552 - Set IP address <a href="https://reprap.org/wiki/G-code#M552:_Set_IP_address.2C_enable.2Fdisable_network_interface">M552: Set IP address, enable/disable network interface"</a>
+    Sets the printer IP address that is shown in the support menu. Designed to be used with the help of host software.
+    If P is not specified nothing happens.
+    If the structure of the IP address is invalid, 0.0.0.0 is assumed and nothing is shown on the screen in the Support menu.
+    #### Usage
+    
+        M552 [ P<IP_address> ]
+    
+    #### Parameters
+    - `P` - The IP address in xxx.xxx.xxx.xxx format. Eg: P192.168.1.14
+	*/
     case 552:
     {
         if (code_seen('P'))