[docs] Organize driver & feature docs into subfolders (#23848)

Co-authored-by: Nick Brassel <nick@tzarc.org>

docs/features/led_indicators.md

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+# LED Indicators
+
+::: tip
+LED indicators on split keyboards will require state information synced to the slave half (e.g. `#define SPLIT_LED_STATE_ENABLE`). See [data sync options](split_keyboard#data-sync-options) for more details.
+:::
+
+QMK provides methods to read 5 of the LEDs defined in the HID spec:
+
+* Num Lock
+* Caps Lock
+* Scroll Lock
+* Compose
+* Kana
+
+There are three ways to get the lock LED state:
+* Configuration options in `config.h`
+* Implement `led_update_*` function
+* Call `led_t host_keyboard_led_state()`
+
+::: warning
+The `host_keyboard_led_state()` may reflect an updated state before `led_update_user()` is called.
+:::
+
+Two deprecated functions that provide the LED state as `uint8_t`:
+
+* `uint8_t led_set_user(uint8_t usb_led)`
+* `uint8_t host_keyboard_leds()`
+
+## Configuration Options
+
+To configure the indicators, `#define` these in your `config.h`:
+
+|Define               |Default      |Description                                |
+|---------------------|-------------|-------------------------------------------|
+|`LED_NUM_LOCK_PIN`   |*Not defined*|The pin that controls the `Num Lock` LED   |
+|`LED_CAPS_LOCK_PIN`  |*Not defined*|The pin that controls the `Caps Lock` LED  |
+|`LED_SCROLL_LOCK_PIN`|*Not defined*|The pin that controls the `Scroll Lock` LED|
+|`LED_COMPOSE_PIN`    |*Not defined*|The pin that controls the `Compose` LED    |
+|`LED_KANA_PIN`       |*Not defined*|The pin that controls the `Kana` LED       |
+|`LED_PIN_ON_STATE`   |`1`          |The state of the indicator pins when the LED is "on" - `1` for high, `0` for low|
+
+Unless you are designing your own keyboard, you generally should not need to change the above config options.
+
+## LED update function
+
+When the configuration options do not provide enough flexibility, the following callbacks allow custom control of the LED behavior. These functions will be called when one of those 5 LEDs changes state: 
+
+* Keyboard/revision: `bool led_update_kb(led_t led_state)`
+* Keymap: `bool led_update_user(led_t led_state)`
+
+Both receives LED state as a struct parameter. Returning `true` in `led_update_user()` will allow the keyboard level code in `led_update_kb()` to run as well. Returning `false` will override the keyboard level code, depending on how the keyboard level function is set up.
+
+::: tip
+This boolean return type of `led_update_user` allows for overriding keyboard LED controls, and is thus recommended over the void `led_set_user` function.
+:::
+
+### Example of keyboard LED update implementation
+
+This is a template indicator function that can be implemented on keyboard level code:
+
+```c
+bool led_update_kb(led_t led_state) {
+    bool res = led_update_user(led_state);
+    if(res) {
+        // gpio_write_pin sets the pin high for 1 and low for 0.
+        // In this example the pins are inverted, setting
+        // it low/0 turns it on, and high/1 turns the LED off.
+        // This behavior depends on whether the LED is between the pin
+        // and VCC or the pin and GND.
+        gpio_write_pin(B0, !led_state.num_lock);
+        gpio_write_pin(B1, !led_state.caps_lock);
+        gpio_write_pin(B2, !led_state.scroll_lock);
+        gpio_write_pin(B3, !led_state.compose);
+        gpio_write_pin(B4, !led_state.kana);
+    }
+    return res;
+}
+```
+
+### Example of user LED update implementation
+
+This is an incomplete example will play a sound if Caps Lock is turned on or off. It returns `true` to allow keyboard LED function to maintain their state.
+
+```c
+#ifdef AUDIO_ENABLE
+  float caps_on[][2] = SONG(CAPS_LOCK_ON_SOUND);
+  float caps_off[][2] = SONG(CAPS_LOCK_OFF_SOUND);
+#endif
+
+bool led_update_user(led_t led_state) {
+    #ifdef AUDIO_ENABLE
+    static uint8_t caps_state = 0;
+    if (caps_state != led_state.caps_lock) {
+        led_state.caps_lock ? PLAY_SONG(caps_on) : PLAY_SONG(caps_off);
+        caps_state = led_state.caps_lock;
+    }
+    #endif
+    return true;
+}
+```
+
+## Host keyboard LED state 
+
+The `host_keyboard_led_state()` function will report the LED state returned from the host computer as `led_t`. This is useful for reading the LED state outside `led_update_*`. For example, you can get the boolean state of Caps Lock from the host with:
+
+```c
+bool caps = host_keyboard_led_state().caps_lock;
+```
+
+## `led_update_ports()`
+
+This function writes the LED state to the actual hardware. Call it manually
+from your `led_update_*()` callbacks to modify the handling of the standard
+keyboard LEDs.
+For example when repurposing a standard LED indicator as layer indicator.
+
+## Setting Physical LED State
+
+Some keyboard implementations provide convenient methods for setting the state of the physical LEDs.
+
+### Ergodox Boards
+
+The Ergodox implementations provide `ergodox_right_led_1`/`2`/`3_on`/`off()` to turn individual LEDs on or off, as well as `ergodox_right_led_on`/`off(uint8_t led)` to turn them on or off by their index.
+
+In addition, it is possible to specify the brightness level of all LEDs with `ergodox_led_all_set(uint8_t n)`; of individual LEDs with `ergodox_right_led_1`/`2`/`3_set(uint8_t n)`; or by index with `ergodox_right_led_set(uint8_t led, uint8_t n)`.
+
+Ergodox boards also define `LED_BRIGHTNESS_LO` for the lowest brightness and `LED_BRIGHTNESS_HI` for the highest brightness (which is the default).