DRM DEVICE TREE 解析

总的drm device结构如下:

// rockchip drm core 设备
display_subsystem: display-subsystem {
    compatible = "rockchip,display-subsystem";
    ports = <&vopl_out>, <&vopb_out>;
};

// 显示控制器vop驱动
vopl: vop@ff8f0000 {
    compatible = "rockchip,rk3399-vop-lit";
    vopl_out: port {
        vopl_out_edp: endpoint@1 {
            reg = <1>;
            remote-endpoint = <&edp_in_vopl>;
        };
    };
};

// edp驱动
edp: edp@ff970000 {
    compatible = "rockchip,rk3399-edp";
    ports {
        edp_in: port@0 {
            edp_in_vopl: endpoint@1 {
                reg = <1>;
                remote-endpoint = <&vopl_out_edp>;
            };
        };
        edp_out: port@1 {
            edp_out_panel: endpoint@0 {
                reg = <0>;
                remote-endpoint = <&panel_in_edp>;
            };
        };
    };
};

edp屏驱动
edp_panel: edp-panel {
    compatible = "lg,lp079qx1-sp0v", "panel-simple";
    //通过短字符串"lg,lp079qx1-sp0v"来匹配写死在kernel源码中的timing

    ports {
        panel_in_edp: endpoint {
            remote-endpoint = <&edp_out_panel>;
        };
    };
};