Document BM8563 RTC configuration for M5Stack-Core2

src/docs/devices/M5Stack-Core2/index.md

@@ -5,7 +5,7 @@ type: misc
 standard: global
 board: esp32
 project-url: https://docs.m5stack.com/en/core/core2
-made-for-esphome: False
+made-for-esphome: false
 difficulty: 2
 ---
 
@@ -194,11 +194,40 @@ binary_sensor:
 #         data: !lambda return startup_raw;
 ```
 
+## RTC
+
+[BM8563 Time Source](https://esphome.io/components/time/bm8563/)
+
+```yaml
+# First block - hardware definition only
+time:
+  - platform: bm8563
+    # repeated synchronization is not necessary unless the external RTC
+    # is much more accurate than the internal clock
+    update_interval: never
+```
+
+```yaml
+# Second block - more complex example with integration
+time:
+  - platform: bm8563
+    update_interval: never
+  - platform: homeassistant
+    on_time_sync:
+      then:
+        bm8563.write_time:
+
+esphome:
+  on_boot:
+    then:
+      bm8563.read_time:
+```
+
 ## Notes
 
 - **Display**: works reliably with `mipi_spi` (ILI9341)
 - **Touchscreen**: works well with `ft63x6`, including virtual button regions (A/B/C)
 - **MPU6886 IMU**: provides data for accelerometer, gyroscope, and temperature. Temperature readings are erratic and inaccurate
 - **Speaker**: didn't work, but some config is provided
 - **Microphone**: untested
-- **BM8563 RTC**: not configured, no ESPHome component exists for it
+- **BM8563 RTC**: ESPHome component exists for version >=2025.11.2.