core/homeassistant/components/modbus/icons.json

{
  "services": {
    "reload": {
      "service": "mdi:reload"
    },
    "write_coil": {
      "service": "mdi:pencil"
    },
    "write_register": {
      "service": "mdi:database-edit"
    },
    "stop": {
      "service": "mdi:stop"
    },
    "restart": {
      "service": "mdi:restart"
    }
  }
}