pvmfw: parse and validate incoming device tree

Validate the incoming device tree and parse it into DeviceTreeInfo. No
modification to the device tree is made with this CL. The follow-up CL
will patch the embedded device tree template with DeviceTreeInfo.

Bug: 249054080
Test: run protected VM and see the log message from pvmfw

Change-Id: Ie55fa4ba70c807c729407c136c5b7d262473dae5
diff --git a/libs/fdtpci/src/lib.rs b/libs/fdtpci/src/lib.rs
index e32e16d..96d98d6 100644
--- a/libs/fdtpci/src/lib.rs
+++ b/libs/fdtpci/src/lib.rs
@@ -197,24 +197,32 @@
     Ok(memory_address..memory_address + memory_size)
 }
 
+/// Encodes memory flags of a PCI range
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
-struct PciMemoryFlags(u32);
+pub struct PciMemoryFlags(pub u32);
 
 impl PciMemoryFlags {
+    /// Returns whether this PCI range is prefetchable
     pub fn prefetchable(self) -> bool {
         self.0 & 0x80000000 != 0
     }
 
+    /// Returns the type of this PCI range
     pub fn range_type(self) -> PciRangeType {
         PciRangeType::from((self.0 & 0x3000000) >> 24)
     }
 }
 
+/// Type of a PCI range
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
-enum PciRangeType {
+pub enum PciRangeType {
+    /// Range represents the PCI configuration space
     ConfigurationSpace,
+    /// Range is on IO space
     IoSpace,
+    /// Range is on 32-bit MMIO space
     Memory32,
+    /// Range is on 64-bit MMIO space
     Memory64,
 }