diff --git a/esphome/components/ethernet/__init__.py b/esphome/components/ethernet/__init__.py
index b4b1fcd9f6..e1ed327fb9 100644
--- a/esphome/components/ethernet/__init__.py
+++ b/esphome/components/ethernet/__init__.py
@@ -434,10 +434,13 @@ def _final_validate_rmii_pins(config: ConfigType) -> None:
 
     # Check all used pins against RMII reserved pins
     for pin_list in pins.PIN_SCHEMA_REGISTRY.pins_used.values():
-        for pin_path, _, pin_config in pin_list:
+        for pin_path, pin_device, pin_config in pin_list:
             pin_num = pin_config.get(CONF_NUMBER)
             if pin_num not in rmii_pins:
                 continue
+            # Skip if pin is not directly on ESP, but at some expander (device set to something else than 'None')
+            if pin_device is not None:
+                continue
             # Found a conflict - show helpful error message
             pin_function = rmii_pins[pin_num]
             component_path = ".".join(str(p) for p in pin_path)
diff --git a/esphome/core/progmem.h b/esphome/core/progmem.h
index 67131fd113..f9508945e8 100644
--- a/esphome/core/progmem.h
+++ b/esphome/core/progmem.h
@@ -1,16 +1,16 @@
 #pragma once
 
 // Platform-agnostic macros for PROGMEM string handling
-// On ESP32 (both Arduino and IDF): Use plain strings (no PROGMEM)
 // On ESP8266/Arduino: Use Arduino's F() macro for PROGMEM strings
+// On other platforms: Use plain strings (no PROGMEM)
 
-#ifdef USE_ESP32
-#define ESPHOME_F(string_literal) (string_literal)
-#define ESPHOME_PGM_P const char *
-#define ESPHOME_strncpy_P strncpy
-#else
-// ESP8266 and other Arduino platforms use Arduino macros
+#ifdef USE_ESP8266
+// ESP8266 uses Arduino macros
 #define ESPHOME_F(string_literal) F(string_literal)
 #define ESPHOME_PGM_P PGM_P
 #define ESPHOME_strncpy_P strncpy_P
+#else
+#define ESPHOME_F(string_literal) (string_literal)
+#define ESPHOME_PGM_P const char *
+#define ESPHOME_strncpy_P strncpy
 #endif
diff --git a/tests/components/ethernet/test-lan8720-with-expander.esp32-idf.yaml b/tests/components/ethernet/test-lan8720-with-expander.esp32-idf.yaml
new file mode 100644
index 0000000000..09da8d90d9
--- /dev/null
+++ b/tests/components/ethernet/test-lan8720-with-expander.esp32-idf.yaml
@@ -0,0 +1,15 @@
+<<: !include common-lan8720.yaml
+
+sn74hc165:
+  - id: sn74hc165_hub
+    clock_pin: GPIO13
+    data_pin: GPIO14
+    load_pin: GPIO15
+    sr_count: 3
+
+binary_sensor:
+  - platform: gpio
+    pin:
+      sn74hc165: sn74hc165_hub
+      number: 19
+    id: relay_2