[mdns] Extract common Arduino mDNS registration to shared header

esphome/components/mdns/mdns_arduino.h

@@ -0,0 +1,42 @@
+#pragma once
+#include "esphome/core/defines.h"
+
+// Common Arduino mDNS registration for RP2040 and LibreTiny
+#if defined(USE_MDNS) && (defined(USE_RP2040) || defined(USE_LIBRETINY))
+
+#include "esphome/core/application.h"
+#include "mdns_component.h"
+
+namespace esphome::mdns {
+
+/// Register mDNS services using Arduino-style mDNS library (RP2040/LibreTiny)
+/// @param services The services to register
+inline void register_arduino_mdns(MDNSComponent *, StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services) {
+  MDNS.begin(App.get_name().c_str());
+
+  for (const auto &service : services) {
+    // Strip the leading underscore from the proto and service_type. While it is
+    // part of the wire protocol to have an underscore, and for example ESP-IDF
+    // expects the underscore to be there, the RP2040/LibreTiny mDNS
+    // implementations always add the underscore themselves.
+    auto *proto = MDNS_STR_ARG(service.proto);
+    while (*proto == '_') {
+      proto++;
+    }
+
+    auto *service_type = MDNS_STR_ARG(service.service_type);
+    while (*service_type == '_') {
+      service_type++;
+    }
+
+    uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
+    MDNS.addService(service_type, proto, port);
+    for (const auto &record : service.txt_records) {
+      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key), MDNS_STR_ARG(record.value));
+    }
+  }
+}
+
+}  // namespace esphome::mdns
+
+#endif