Add BMI270 sensor documentation

- Add documentation for BMI270 accelerometer/gyroscope sensor
- Include configuration examples and sensor options
- Add BMI270 to Motion sensors section in component index
- Based on similar BMI160 sensor structure

Refs: esphome/esphome#11958

Author: claude

content/components/_index.md

@@ -506,6 +506,7 @@ Sensors are organized into categories; if a given sensor fits into more than one
 {{< imgtable >}}
 "APDS9960","components/sensor/apds9960","apds9960.jpg","Colour & Gesture"
 "BMI160","components/sensor/bmi160","bmi160.jpg","Accelerometer & Gyroscope"
+"BMI270","components/sensor/bmi270","bmi270.jpg","Accelerometer & Gyroscope"
 "LD2410","components/sensor/ld2410","ld2410.jpg","Motion & Presence"
 "LD2412","components/sensor/ld2412","ld2412.jpg","Motion & Presence"
 "LD2420","components/sensor/ld2420","ld2420.jpg","Motion & Presence"

content/components/sensor/bmi270.md

@@ -0,0 +1,76 @@
+---
+description: "Instructions for setting up BMI270 Accelerometer and Gyroscope sensors."
+title: "BMI270 Accelerometer/Gyroscope Sensor"
+params:
+  seo:
+    description: Instructions for setting up BMI270 Accelerometer and Gyroscope sensors.
+    image: bmi270.jpg
+---
+
+The `bmi270` sensor platform allows you to use your BMI270 Accelerometer/Gyroscope
+([datasheet](https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bmi270-ds000.pdf)) sensors with ESPHome. The [I²C Bus](/components/i2c) is required to be set up in your configuration for this
+sensor to work.
+
+The BMI270 is a low-power 6-axis inertial measurement unit (IMU) from Bosch Sensortec, designed for wearables and other battery-powered applications. It offers improved power efficiency and features compared to its predecessor, the BMI160.
+
+This component only does some basic filtering and no calibration. Due to the complexity of this sensor and the amount
+of possible configuration options, you should probably create an {{< docref "/components/external_components" "external component" >}}
+by copying and modifying the existing code if you want a specific new feature. Supporting all possible use cases would
+be quite hard.
+
+```yaml
+# Example configuration entry
+sensor:
+  - platform: bmi270
+    address: 0x68
+    update_interval: 60s
+    acceleration_x:
+      name: "BMI270 Accel X"
+    acceleration_y:
+      name: "BMI270 Accel Y"
+    acceleration_z:
+      name: "BMI270 Accel Z"
+    gyroscope_x:
+      name: "BMI270 Gyro X"
+    gyroscope_y:
+      name: "BMI270 Gyro Y"
+    gyroscope_z:
+      name: "BMI270 Gyro Z"
+    temperature:
+      name: "BMI270 Temperature"
+```
+
+## Configuration variables
+
+- **address** (*Optional*, int): Manually specify the I²C address of the sensor. Defaults to `0x68`, may also be `0x69`.
+- **acceleration_x** (*Optional*): Use the X-Axis of the Accelerometer. All options from
+  [Sensor](/components/sensor).
+
+- **acceleration_y** (*Optional*): Use the Y-Axis of the Accelerometer. All options from
+  [Sensor](/components/sensor).
+
+- **acceleration_z** (*Optional*): Use the Z-Axis of the Accelerometer. All options from
+  [Sensor](/components/sensor).
+
+- **gyroscope_x** (*Optional*): Use the X-Axis of the Gyroscope. All options from
+  [Sensor](/components/sensor).
+
+- **gyroscope_y** (*Optional*): Use the Y-Axis of the Gyroscope. All options from
+  [Sensor](/components/sensor).
+
+- **gyroscope_z** (*Optional*): Use the Z-Axis of the Gyroscope. All options from
+  [Sensor](/components/sensor).
+
+- **temperature** (*Optional*): Use the internal temperature of the sensor. All options from
+  [Sensor](/components/sensor).
+
+- **update_interval** (*Optional*, [Time](/guides/configuration-types#time)): The interval to check the sensor. Defaults to `60s`.
+
+- **id** (*Optional*, [ID](/guides/configuration-types#id)): Manually specify the ID used for code generation.
+
+## See Also
+
+- [Sensor Filters](/components/sensor#sensor-filters)
+- {{< docref "bmi160/" >}}
+- {{< apiref "bmi270/bmi270.h" "bmi270/bmi270.h" >}}
+- [Bosch BMI270 Product Page](https://www.bosch-sensortec.com/products/motion-sensors/imus/bmi270/)