rockchip: rk3399: Add ROC-RK3399-PC support

Add initial support for ROC-RK3399-PC board.

Specification
- Rockchip RK3399
- LPDDR4 4GiB
- eMMC slot
- SD card slot
- RTL8211E 1Gbps
- HDMI Out, DP, MIPI DSI/CSI, EDP
- PCIe M.2
- USB 2.0, USB-3.0
- USB C Type

Commit details of rk3399-roc-pc.dts sync from Linux v5.2:
"arm64: dts: rockchip: add support for ROC-RK3399-PC board"
(sha1: 8bb878cf20ae10809c36db96993bfce7026d062b)

Signed-off-by: Levin Du <djw@t-chip.com.cn>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3399-roc-pc-u-boot.dtsi b/arch/arm/dts/rk3399-roc-pc-u-boot.dtsi
new file mode 100644
index 0000000..77d5cf5
--- /dev/null
+++ b/arch/arm/dts/rk3399-roc-pc-u-boot.dtsi
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Levin Du <djw@t-chip.com.cn>
+ */
+
+#include "rk3399-u-boot.dtsi"
+#include "rk3399-sdram-lpddr4-100.dtsi"
+
+/ {
+	chosen {
+		u-boot,spl-boot-order = "same-as-spl", &sdhci, &sdmmc;
+	};
+};
+
+&vdd_log {
+	regulator-min-microvolt = <430000>;
+	regulator-init-microvolt = <950000>;
+};