[mdns] Add mDNS to Zephyr and nRF52 (#16924)

Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>

esphome/components/mdns/mdns_component.cpp

@@ -100,7 +100,7 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
     if (!friendly_name_empty) {
       txt_count++;  // friendly_name
     }
-#if defined(USE_ESP8266) || defined(USE_ESP32) || defined(USE_RP2040) || defined(USE_LIBRETINY)
+#if defined(USE_ESP8266) || defined(USE_ESP32) || defined(USE_RP2040) || defined(USE_LIBRETINY) || defined(USE_NRF52)
     txt_count++;  // platform
 #endif
 #if defined(USE_WIFI) || defined(USE_ETHERNET) || defined(USE_OPENTHREAD)
@@ -141,6 +141,9 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
     txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_RP2040)});
 #elif defined(USE_LIBRETINY)
     txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(lt_cpu_get_model_name())});
+#elif defined(USE_NRF52)
+    MDNS_STATIC_CONST_CHAR(PLATFORM_NRF52, "nRF52");
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_NRF52)});
 #endif
 
     txt_records.push_back({MDNS_STR(TXT_BOARD), MDNS_STR(VALUE_BOARD)});

esphome/components/mdns/mdns_zephyr.cpp

@@ -2,13 +2,20 @@
 #if defined(USE_ZEPHYR) && defined(USE_MDNS)
 
 #include "mdns_component.h"
-#include "esphome/core/log.h"
 
 namespace esphome::mdns {
 
-static const char *const TAG = "mdns.zephyr";
+#ifdef USE_MDNS_STORE_SERVICES
+// Zephyr has no local IP mDNS responder. When a consumer (ex. the OpenThread SRP
+// client) enables service storage, it reads the compiled records via get_services()
+// and advertises them itself. We only need to compile and store the records here.
+static void register_zephyr(MDNSComponent *, StaticVector<MDNSService, MDNS_SERVICE_COUNT> &) {}
 
-void MDNSComponent::setup() { ESP_LOGW(TAG, "mDNS is not implemented for Zephyr"); }
+void MDNSComponent::setup() { this->setup_buffers_and_register_(register_zephyr); }
+#else
+// No responder and nothing consuming the records, so skip the boot-time compile.
+void MDNSComponent::setup() {}
+#endif
 
 void MDNSComponent::on_shutdown() {}
 

tests/components/mdns/test.nrf52-adafruit.yaml

@@ -0,0 +1,4 @@
+network:
+  enable_ipv6: true
+
+mdns: