gpiolib: of: add a quirk for legacy names in Mediatek mt2701-cs42448

The driver is using non-standard "i2s1-in-sel-gpio1" and
"i2s1-in-sel-gpio2" names to describe its gpios. In preparation to
converting to the standard naming (i2s1-in-sel-gpios) and switching the
driver to gpiod API add a quirk to gpiolib to keep compatibility with
existing DTSes.
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpiolib-of.c

@@ -488,6 +488,38 @@ static struct gpio_desc *of_find_usb_gpio(struct device_node *np,
 	return of_get_named_gpiod_flags(np, con_id, idx, of_flags);
 }
 
+static struct gpio_desc *of_find_mt2701_gpio(struct device_node *np,
+					     const char *con_id,
+					     unsigned int idx,
+					     enum of_gpio_flags *of_flags)
+{
+	struct gpio_desc *desc;
+	const char *legacy_id;
+
+	if (!IS_ENABLED(CONFIG_SND_SOC_MT2701_CS42448))
+		return ERR_PTR(-ENOENT);
+
+	if (!of_device_is_compatible(np, "mediatek,mt2701-cs42448-machine"))
+		return ERR_PTR(-ENOENT);
+
+	if (!con_id || strcmp(con_id, "i2s1-in-sel"))
+		return ERR_PTR(-ENOENT);
+
+	if (idx == 0)
+		legacy_id = "i2s1-in-sel-gpio1";
+	else if (idx == 1)
+		legacy_id = "i2s1-in-sel-gpio2";
+	else
+		return ERR_PTR(-ENOENT);
+
+	desc = of_get_named_gpiod_flags(np, legacy_id, 0, of_flags);
+	if (!gpiod_not_found(desc))
+		pr_info("%s is using legacy gpio name '%s' instead of '%s-gpios'\n",
+			of_node_full_name(np), legacy_id, con_id);
+
+	return desc;
+}
+
 typedef struct gpio_desc *(*of_find_gpio_quirk)(struct device_node *np,
 						const char *con_id,
 						unsigned int idx,
@@ -498,6 +530,7 @@ static const of_find_gpio_quirk of_find_gpio_quirks[] = {
 	of_find_regulator_gpio,
 	of_find_arizona_gpio,
 	of_find_usb_gpio,
+	of_find_mt2701_gpio,
 	NULL
 };