[openthread] Document output_power

[schdro]

Description

Add output_power to openthread component.

• Basically same semantic as same config key output_power has in other components like wifi.
• More focus was put into stressing the responsibility of complying to regulatory limits. Which might also be topic to mention in other components like wifi.
• Trivia: Some vendors like Nordic Semiconductor seem to impose much lower hardware limits like 7dBm/8dBm (except for setups with external FEM). Espressif obviously wants to leave room for making use of regulative maximum, leaving also room for risk.
• Homeassistant OTBR addon as parent/router currently uses default tx power of 6dB after own analysis of others to avoid "asymmetric link quality": https://github.com/home-assistant/addons/blob/master/openthread_border_router/rootfs/etc/s6-overlay/scripts/otbr-agent-configure.sh
• For wifi, also option of setting region at radio stack may allow to add further controls. However, for Thread / 802.15.4 did not find any radio platform implementation of otPlatRadioSetRegion (not ESP32 via ESP IDF nor nRF) as of now, i.e. error code OT_ERROR_NOT_IMPLEMENTED. Therefore, currently unreasonable to add region setting code into ESPHome.
• OpenThread API otPlatRadioSetTransmitPower "only" allows setting integer values, unlike e.g. wifi allowing float/halfsteps.

Related issue (if applicable): fixes

Pull request in esphome with YAML changes (if applicable):

• [openthread] Add tx power option esphome#14200

Checklist

• I am merging into next because this is new documentation that has a matching pull-request in esphome as linked above.
  or

• I am merging into current because this is a fix, change and/or adjustment in the current documentation and is not for a new component or feature.

• Link added in /src/content/docs/components/index.mdx when creating new documents for new components or cookbook.

New Component Images

If you are adding a new component to ESPHome, you can automatically generate a standardized black and white component name image for the documentation.

To generate a component image:

1. Comment on this pull request with the following command, replacing component_name with your component name in lower_case format with underscores (e.g., bme280, sht3x, dallas_temp):

   @esphomebot generate image component_name
   

2. The ESPHome bot will respond with a downloadable ZIP file containing the SVG image.

3. Extract the SVG file and place it in the /public/images/ folder of this repository.

4. Use the image in your component's index table entry in /src/content/docs/components/index.mdx.

Example: For a component called "DHT22 Temperature Sensor", use:

@esphomebot generate image dht22

Note: All images used in ImgTable components must be placed in /public/images/ as the component resolves them to absolute paths.

[netlify]

✅ Deploy Preview for esphome ready!

Name	Link
🔨 Latest commit	4197d2b
🔍 Latest deploy log	https://app.netlify.com/projects/esphome/deploys/69a33236e52e1400087fd102
😎 Deploy Preview	https://deploy-preview-6175--esphome.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.