chore: import upstream snapshot with attribution

components/esp_stdio/linux/esp_stdio_linux.c

@@ -0,0 +1,54 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <termios.h>
+#include <assert.h>
+#include "sdkconfig.h"
+#include "esp_stdio_linux.h"
+
+static struct termios s_orig_termios;
+
+/**
+ * This function restores the original terminal settings.
+ */
+static void disable_raw_mode(void)
+{
+    assert(tcsetattr(STDIN_FILENO, TCSAFLUSH, &s_orig_termios) == 0);
+}
+
+void linux_vfs_dev_port_deinit(linux_port_config_t *config)
+{
+    (void)config;
+}
+
+esp_err_t linux_vfs_dev_port_init(linux_port_config_t *config)
+{
+    (void)config;
+
+    // Set stdin to unbuffered
+    setvbuf(stdin, NULL, _IONBF, 0);
+
+    const int stdin_fileno = fileno(stdin);
+
+    if (isatty(stdin_fileno)) {
+        // Use Termios driver to activate CR-NL translation and deactivate echo and canonical mode
+        assert(tcgetattr(stdin_fileno, &s_orig_termios) == 0);
+        struct termios raw = s_orig_termios;
+        raw.c_iflag |= ICRNL; // we translate to NL because linenoise expects NL
+        raw.c_lflag &= ~(ECHO | ICANON); // turn off echo and canonical mode
+        assert(tcsetattr(stdin_fileno, TCSAFLUSH, &raw) == 0);
+
+        // Make sure user does not end up with a broken terminal
+        assert(atexit(disable_raw_mode) == 0);
+    } else {
+        // Flush input
+        assert(fflush(stdin) == 0);
+    }
+
+    return ESP_OK;
+}