dts: arm64: qcom: sdm845: add SLPI FastRPC support

Qualcomm SDM845 SoC features a SLPI DSP which uses FastRPC through
an allocated memory region to load files from the host filesystem
such as sensor configuration files.

Add a FastRPC node at /dev/fastrpc-sdsp and a DMA region, similar to
downstream, to allow userspace to communicate with the SLPI via the
FastRPC interface for initializing the sensors on the SLPI.

Signed-off-by: Dylan Van Assche <me@dylanvanassche.be>

arch/arm64/boot/dts/qcom/sdm845.dtsi

@@ -870,6 +870,14 @@
 			size = <0 0x4000>;
 			no-map;
 		};
+
+		fastrpc_mem: fastrpc {
+			compatible = "shared-dma-pool";
+			reusable;
+			alloc-ranges = <0 0x00000000 0 0xffffffff>;
+			alignment = <0 0x400000>;
+			size = <0 0x1000000>;
+		};
 	};
 
 	adsp_pas: remoteproc-adsp {
@@ -3333,6 +3341,22 @@
 				label = "dsps";
 				qcom,remote-pid = <3>;
 				mboxes = <&apss_shared 24>;
+
+				fastrpc {
+					compatible = "qcom,fastrpc";
+					qcom,glink-channels = "fastrpcglink-apps-dsp";
+					label = "sdsp";
+					qcom,non-secure-domain;
+					qcom,vmids = <0x3 0xF 0x5 0x6>;
+					memory-region = <&fastrpc_mem>;
+					qcom,assign-all-mem;
+					#address-cells = <1>;
+					#size-cells = <0>;
+
+					compute-cb {
+						compatible = "qcom,fastrpc-compute-cb";
+					};
+				}
 			};
 		};