dt-bindings: soc: qcom: apr: Add protection domain bindings

Qualcomm SoCs (starting with MSM8998) allow for multiple protection
domains (PDs) to run on the same Q6 sub-system. This allows for
services like AVS AUDIO to have their own separate address space and
crash/recover without disrupting the other PDs running on the same Q6
ADSP. Add "qcom,protection-domain" bindings to capture the dependencies
between the APR service and the PD on which the apr service runs.

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Link: https://lore.kernel.org/r/20200312120842.21991-3-sibis@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Documentation/devicetree/bindings/soc/qcom/qcom,apr.txt

@@ -45,6 +45,18 @@ by the individual bindings for the specific service
 			12 - Ultrasound stream manager.
 			13 - Listen stream manager.
 
+- qcom,protection-domain
+	Usage: optional
+	Value type: <stringlist>
+	Definition: Must list the protection domain service name and path
+		    that the particular apr service has a dependency on.
+	Possible values are :
+			"avs/audio", "msm/adsp/audio_pd".
+			"kernel/elf_loader", "msm/modem/wlan_pd".
+			"tms/servreg", "msm/adsp/audio_pd".
+			"tms/servreg", "msm/modem/wlan_pd".
+			"tms/servreg", "msm/slpi/sensor_pd".
+
 = EXAMPLE
 The following example represents a QDSP based sound card on a MSM8996 device
 which uses apr as communication between Apps and QDSP.
@@ -82,3 +94,41 @@ which uses apr as communication between Apps and QDSP.
 			...
 		};
 	};
+
+= EXAMPLE 2
+The following example represents a QDSP based sound card with protection domain
+dependencies specified. Here some of the apr services are dependent on services
+running on protection domain hosted on ADSP/SLPI remote processors while others
+have no such dependency.
+
+	apr {
+		compatible = "qcom,apr-v2";
+		qcom,glink-channels = "apr_audio_svc";
+		qcom,apr-domain = <APR_DOMAIN_ADSP>;
+
+		q6core {
+			compatible = "qcom,q6core";
+			reg = <APR_SVC_ADSP_CORE>;
+		};
+
+		q6afe: q6afe {
+			compatible = "qcom,q6afe";
+			reg = <APR_SVC_AFE>;
+			qcom,protection-domain = "avs/audio", "msm/adsp/audio_pd";
+			...
+		};
+
+		q6asm: q6asm {
+			compatible = "qcom,q6asm";
+			reg = <APR_SVC_ASM>;
+			qcom,protection-domain = "tms/servreg", "msm/slpi/sensor_pd";
+			...
+		};
+
+		q6adm: q6adm {
+			compatible = "qcom,q6adm";
+			reg = <APR_SVC_ADM>;
+			qcom,protection-domain = "avs/audio", "msm/adsp/audio_pd";
+			...
+		};
+	};