Add support for YAML encoded output

YAML encoded DT is useful for validation of DTs using binding schemas.

The YAML encoding is an intermediate format used for validation and
is therefore subject to change as needed. The YAML output is dependent
on DTS input with type information preserved.

Signed-off-by: Grant Likely <grant.likely@arm.com>
[robh: make YAML support optional, build fixes, Travis CI test,
 preserve type information in paths and phandles]
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/run_tests.sh

@@ -568,6 +568,14 @@ dtc_tests () {
         run_wrap_test cmp $tree $tree.test.dts
     done
 
+    # Check -Oyaml output
+    if pkg-config --exists yaml-0.1; then
+            for tree in type-preservation; do
+                run_dtc_test -I dts -O yaml -o $tree.test.dt.yaml $tree.dts
+                run_wrap_test cmp $tree.dt.yaml $tree.test.dt.yaml
+            done
+    fi
+
     # Check version conversions
     for tree in test_tree1.dtb ; do
 	 for aver in 1 2 3 16 17; do

tests/type-preservation.dt.yaml

@@ -0,0 +1,20 @@
+---
+- '#address-cells': [[0x1]]
+  '#size-cells': [[0x0]]
+  subnode@1:
+    compatible: ["subnode1"]
+    reg: [[0x1]]
+    int-array: [[0x0, 0x1], [0x2, 0x3]]
+    int8: [!u8 [0x56]]
+    int8-array: [!u8 [0x0, 0x12, 0x34, 0x56]]
+    int16: [!u16 [0x3210]]
+    int16-array: [!u16 [0x1234, 0x5678, 0x90ab, 0xcdef]]
+    int16-matrix: [!u16 [0x1234, 0x5678], [0x90ab, 0xcdef]]
+    int64: [!u64 [0x200000000]]
+    int64-array: [!u64 [0x100000000, 0x0]]
+    a-string-with-nulls: ["foo\0bar", "baz"]
+    subsubnode:
+      compatible: ["subsubnode1", "subsubnode"]
+      subsubsubnode:
+        compatible: ["subsubsubnode1", [0x1234], "subsubsubnode"]
+...