drivers/gfx/nvidia: Add driver for NVIDIA GPU

Add a driver for laptops with NVIDIA Optimus (hybrid) graphics. The
driver provides ACPI support for dynamically powering on and off the
GPU, and a function for enabling the GPU power in romstage.

Tested on system76/gaze15.

References:
- DG-09845-001: NVIDIA GN20/QN20 Hardware Design Guide
- DG-09954-001: NVIDIA GN20/QN20 Software Design Guide

Change-Id: I2dec7aa2c8db7994f78a7cc1220502676e248465
Signed-off-by: Jeremy Soller <jeremy@system76.com>
Signed-off-by: Tim Crawford <tcrawford@system76.com>

src/drivers/gfx/nvidia/gpu.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _DRIVERS_GFX_NVIDIA_GPU_H_
+#define _DRIVERS_GFX_NVIDIA_GPU_H_
+
+#include <stdbool.h>
+
+struct nvidia_gpu_config {
+	/* GPIO for GPU_PWR_EN */
+	unsigned int power_gpio;
+	/* GPIO for GPU_RST# */
+	unsigned int reset_gpio;
+	/* Enable or disable GPU power */
+	bool enable;
+};
+
+void nvidia_set_power(const struct nvidia_gpu_config *config);
+
+#endif /* _DRIVERS_NVIDIA_GPU_H_ */