docs/core: align LED_BUILTIN precedence and fix dts examples

Author: soburi

cores/arduino/Arduino.h

@@ -161,7 +161,12 @@
 			DT_MAP_ENTRY_PARENT_BY_IDX(DT_NODELABEL(ZARD_CONNECTOR), gpio_map, i)) +   \
 	DT_MAP_ENTRY_PARENT_SPECIFIER_BY_IDX(DT_NODELABEL(ZARD_CONNECTOR), gpio_map, i, 0)
 
-#if DT_NODE_EXISTS(DT_ALIAS(led0))
+#if DT_NODE_HAS_PROP(DT_PATH(zephyr_user), builtin_led_gpios) &&                                   \
+	(DT_PROP_LEN(DT_PATH(zephyr_user), builtin_led_gpios) > 0)
+#define ZARD_LED_BUILTIN                                                                           \
+	ZARD_GLOBAL_GPIO_OFFSET(DT_PHANDLE_BY_IDX(DT_PATH(zephyr_user), builtin_led_gpios, 0)) +    \
+		DT_PHA_BY_IDX(DT_PATH(zephyr_user), builtin_led_gpios, 0, pin)
+#elif DT_NODE_EXISTS(DT_ALIAS(led0))
 #define ZARD_LED_BUILTIN                                                                           \
 	ZARD_GLOBAL_GPIO_OFFSET(DT_PHANDLE_BY_IDX(DT_ALIAS(led0), gpios, 0)) +                     \
 		DT_PHA_BY_IDX(DT_ALIAS(led0), gpios, 0, pin)

documentation/configuration-guide.md

@@ -134,6 +134,7 @@ Two ways to reach it (**lowest precedence rule first**):
                            /* ---- snip ---- */
                            <ARDUINO_HEADER_R3_D15 0 &ioport1 0 0>;
         };
+    };
     ```
 
 2. **Define `/zephyr,user/digital-pin-gpios`**

documentation/configuration-reference.md

@@ -203,6 +203,7 @@ B. Board devicetree constructs (board-provided defaults)
                            /* ---- snip ---- */
                            <ARDUINO_HEADER_R3_D15 0 &ioport1 0 0>;
         };
+    };
     ```
 
 
@@ -215,9 +216,9 @@ B. Board devicetree constructs (board-provided defaults)
 - **Precedence:**
   - Lower than `/zephyr,user/adc-pin-gpios` (association)
   - Lower than `/zephyr,user/io-channels` (provisioning)
-- **Notes:** `io-channel-map`: left = connector pin id, right = target ADC controller/channel; ADC still needs per-channel config under the ADC device node.
-  - ADC still requires per-channel configuration under the ADC device node,
-    regardless of how the channel list is obtained.
+- **Notes:** `io-channel-map`: left = connector pin id, right = target ADC controller/channel.
+  ADC still requires per-channel configuration under the ADC device node,
+  regardless of how the channel list is obtained.
 - **Example:**
     ```dts
     / {