feat(i2s): supports DMA buffer in PSRAM

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/en/api-reference/peripherals/i2s.rst

@@ -291,6 +291,10 @@ The data transport of the I2S peripheral, including sending and receiving, is re
 
 Both :cpp:func:`i2s_channel_write` and :cpp:func:`i2s_channel_read` are blocking functions. They keeps waiting until the whole source buffer is sent or the whole destination buffer is loaded, unless they exceed the max blocking time, where the error code ``ESP_ERR_TIMEOUT`` returns. To send or receive data asynchronously, callbacks can be registered by  :cpp:func:`i2s_channel_register_event_callback`. Users are able to access the DMA buffer directly in the callback function instead of transmitting or receiving by the two blocking functions. However, please be aware that it is an interrupt callback, so do not add complex logic, run floating operation, or call non-reentrant functions in the callback.
 
+.. only:: SOC_PSRAM_DMA_CAPABLE
+
+    To reduce internal RAM usage, set :cpp:member:`i2s_chan_config_t::dma_buffer_in_psram` to allocate the driver-owned DMA buffers in PSRAM. DMA descriptors remain in internal RAM. The driver returns an error if PSRAM DMA is unavailable or the allocation fails; it does not fall back to internal RAM. When :ref:`CONFIG_I2S_ISR_IRAM_SAFE` is enabled, TX auto-clear cannot be used with PSRAM DMA buffers, and callbacks must not access the DMA buffer while the cache is disabled.
+
 .. only:: SOC_I2S_SUPPORTS_BT_DEST
 
     On {IDF_TARGET_NAME}, when calling :cpp:func:`i2s_new_channel`, you can select the data path for TX and RX separately via :cpp:member:`i2s_chan_config_t::tx_destination` and :cpp:member:`i2s_chan_config_t::rx_destination`. For each direction you can choose either **DMA** or **Bluetooth**: